I wrote this script for everybody who's using EFISTUB to boot but tired of searching for PARTUUIDs, writing out every option or who's simply forgetting the syntax every time a new kernel parameter needs to be added.
The script requires efibootmgr to be installed, which can be done from the script itself if it's not present.
Right click here and "Save as..." (Github raw URL)
Save it to your home folder or any other permissive location
sudo mv ~/mkefistub /usr/bin/mkefistub
sudo chmod +x /usr/bin/mkefistub
Enjoy!
Alternatively you can create /usr/bin/mkefistub before hand and copy/paste the source from here:
# !/bin/bash

# mkefistub - creates new EFI boot menu entries with efibootmgr
# Copyright (C) 2019  Marian Arlt

# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.

# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.

# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.

printf "\nmkefistub - Copyright (C) 2019  Marian Arlt\n"
printf "\nThis program can render your system unbootable in UEFI mode if used incorrectly!"
printf "\nMake sure you know and understand the details of each option before changing them.\n\n\n"

# Check for package dependency
pacman -Qi efibootmgr &> /dev/null
if [[ $? == 1 ]]; then
	printf "This script requires efibootmgr which is not installed on your system.\n"
	printf "Want to install right now? [Y/n]: "
	read -r INSTALLCHOICE
	if [[ ${INSTALLCHOICE} == "n"} ]]; then
		exit
	else
		pacman -S efibootmgr
	fi
fi

# Extract variables from system
BLK=$(blkid)
SDX=$(lsblk | grep ' /$' | sed 's/^.*\(sd.\)\(...*\)/\1/')
DISK=/dev/${SDX}
ROOT=PARTUUID=$(blkid | grep ${DISK}3 | sed 's/^.*PARTUUID=//' | tr -d '"')
# Hard coded variables
PART=1
LABEL=Obarun
LOADER=/vmlinuz-linux

# Provide maximum customization of parameters
printf "\nThe default options are extracted from your system and set to work with a default Obarun Linux install. "
printf "If you customized your install or are using a different operating system make sure that all the parameters will work.\n"
printf "\nShow and/or change any of the defaults? [y/N]: "
read -r DEFAULTCHOICE
if [[ $DEFAULTCHOICE == "y" ]]; then
	while true
	do
		OPTIONS=("--disk $DISK" "--part $PART" "--label \"$LABEL\"" "--loader $LOADER" '--unicode "root='$ROOT'"')
		PS3=$'\nChoose a parameter to change [1-'${# OPTIONS[@ ]}'] or confirm ['$((${# OPTIONS[@ ]}+1))']: '
		select OPT in "${OPTIONS[@ ]}" "Confirm";
		do
			case $REPLY in
				1)	printf "%s" "--disk ";		read -r DISK;		break;;
				2)	printf "%s" "--part ";		read -r PART;		break;;
				3)	printf "%s" "--label ";		read -r LABEL;		break;;
				4)	printf "%s" "--loader ";	read -r LOADER;		break;;
				5)	printf "\n${BLK}\n\nroot=";	read -r ROOT;		break;;
				$((${# OPTIONS[@ ]}+1)) )								break 2;;
				*) printf "$REPLY is not a valid option!\n";		break;;
			esac
		done
	done
fi

# Prompt for swap kernel parameter
printf "\nAdd resume kernel parameter for swap? [y/N]: "
read -r SWAPCHOICE
if [[ $SWAPCHOICE == "y" ]]; then
	printf "\n${BLK}\n\nresume="; read -r SWAP
fi

# Prompt for microcode kernel parameter
printf "\nAdd ucode kernel parameter for microcode? [y/N]: "
read -r UCODECHOICE
if [[ $UCODECHOICE == "y" ]]; then
	OPTIONS=("Intel" "AMD")
	PS3=$'\nPlease choose your platform [1-2]: '
	select OPT in "${OPTIONS[@ ]}";
	do
		UCODE=$(echo "${OPTIONS[($REPLY-1)]}" | sed 's/./\L&/g')
		pacman -Qi ${UCODE}-ucode &> /dev/null
		if [[ $? == 1 ]]; then
			printf "\n\033[1m\033[31m[ERROR]\033[0m ${OPTIONS[($REPLY-1)]} microcode package is not installed!\n"
			OPTIONS=("Ignore and not use parameter" "Exit script")
			PS3=$'\nHow do you want to proceed? [1-2]: '
			select OPT in "${OPTIONS[@ ]}";
			do
				case $REPLY in
					1) break 2;;
					2) printf "\n"; exit
				esac
			done
		fi
		break
	done
fi

# Offer a revision of made changes
printf "\nReview your changes? [y/N]: "
read -r REVIEWCHOICE
if [[ ${REVIEWCHOICE} == "y" ]]; then
	while true
	do
		UCODE=$(echo ${UCODE} | sed 's/./\L&/g')
		OPTIONS=("--disk $DISK" "--part $PART" "--label \"$LABEL\"" "--loader $LOADER" '--unicode "root='$ROOT'"')
		if [[ ${SWAPCHOICE} == "y" ]]; then
			OPTIONS+=('--unicode "resume='${SWAP}'"')
		fi
		if [[ ${UCODECHOICE} == "y" ]]; then
			OPTIONS+=('--unicode "initrd=\'${UCODE}'-ucode.img"')
		fi
		PS3=$'\nChoose a parameter to change [1-'${# OPTIONS[@ ]}'] or confirm ['$((${# OPTIONS[@ ]}+1))']: '
		select OPT in "${OPTIONS[@ ]}" "Confirm";
		do
			if [[ ${SWAPCHOICE} == "y" ]] && [[ ${UCODECHOICE} == "y" ]]; then
				case $REPLY in
					1)	printf "%s" "--disk ";		read -r DISK;		break;;
					2)	printf "%s" "--part ";		read -r PART;		break;;
					3)	printf "%s" "--label ";		read -r LABEL;		break;;
					4)	printf "%s" "--loader ";	read -r LOADER;		break;;
					5)	printf "\n${BLK}\n\nroot=";	read -r ROOT;		break;;
					6)  printf "\n${BLK}\n\nresume=";	read -r SWAP;	break;;
					7)	printf "platform=";			read -r UCODE;		break;;
					$((${# OPTIONS[@ ]}+1)) )								break 2;;
					*) printf "$REPLY is not a valid option!\n";		break;;
				esac
			elif [[ ${SWAPCHOICE} == "y" ]]; then
				case $REPLY in
					1)	printf "%s" "--disk ";		read -r DISK;		break;;
					2)	printf "%s" "--part ";		read -r PART;		break;;
					3)	printf "%s" "--label ";		read -r LABEL;		break;;
					4)	printf "%s" "--loader ";	read -r LOADER;		break;;
					5)	printf "\n${BLK}\n\nroot=";	read -r ROOT;		break;;
					6)  printf "\n${BLK}\n\nresume=";	read -r SWAP;	break;;
					$((${# OPTIONS[@ ]}+1)) )								break 2;;
					*) printf "$REPLY is not a valid option!\n";		break;;
				esac
			elif [[ ${UCODECHOICE} == "y" ]]; then
				case $REPLY in
					1)	printf "%s" "--disk ";		read -r DISK;		break;;
					2)	printf "%s" "--part ";		read -r PART;		break;;
					3)	printf "%s" "--label ";		read -r LABEL;		break;;
					4)	printf "%s" "--loader ";	read -r LOADER;		break;;
					5)	printf "\n${BLK}\n\nroot=";	read -r ROOT;		break;;
					6)  printf "platform=";			read -r UCODE;		break;;
					$((${# OPTIONS[@ ]}+1)) )								break 2;;
					*) printf "$REPLY is not a valid option!\n";		break;;
				esac
			else		
				case $REPLY in
					1)	printf "%s" "--disk ";		read -r DISK;		break;;
					2)	printf "%s" "--part ";		read -r PART;		break;;
					3)	printf "%s" "--label ";		read -r LABEL;		break;;
					4)	printf "%s" "--loader ";	read -r LOADER;		break;;
					5)	printf "\n${BLK}\n\nroot=";	read -r ROOT;		break;;
					$((${# OPTIONS[@ ]}+1)) )								break 2;;
					*) printf "$REPLY is not a valid option!\n";		break;;
				esac
			fi
		done
	done
fi

# Additional kernel parameters
UCODE=$(echo ${UCODE} | sed 's/./\L&/g')
printf "\nInclude additional kernel parameters? [y/N]: "
read -r KERNELCHOICE
if [[ ${KERNELCHOICE} == "y" ]]; then
	printf "\nSeparate multiple parameters with white space.\n"
	read -e KERNELPARAMS
fi

# Gather all conditional parameters
OPTIONALPARAMS=()
if [[ ${SWAPCHOICE} == "y" ]]; then
	OPTIONALPARAMS+=("resume=${SWAP}")
fi
if [[ ${KERNELCHOICE} == "y" ]]; then
	OPTIONALPARAMS+=("${KERNELPARAMS}")
fi
if [[ ${UCODECHOICE} == "y" ]]; then
	OPTIONALPARAMS+=('initrd=\'${UCODE}'-ucode.img')
fi

# Test for existing entry with the same label and create
efibootmgr | grep $LABEL &> /dev/null
if [[ $? == 0 ]]; then
	printf "\n\033[1m\033[31m[WARNING]\033[0m A boot entry with the same label already exists!\n"
	OPTIONS=("Overwrite existing" "Make a new label")
	PS3=$'\nHow do you want to create your entry? [1-2]: '
	select OPT in "${OPTIONS[@ ]}";
	do
		case $REPLY in
			1)	ENTRY=$(efibootmgr | grep $LABEL | sed -r 's/[^0-9]*//g')
				efibootmgr -b ${ENTRY} -B
				printf "\n%s\n" "Removed boot entry with number ${ENTRY}."
				sleep 1
				efibootmgr -c -q -d ${DISK} -p ${PART} -L "${LABEL}" -l ${LOADER} -u 'root='${ROOT}' ro '"${OPTIONALPARAMS[*]}"' initrd=\initramfs-linux.img'
				printf "\n%s\n" "Created entry with the following command:"
				printf "\n%s" 'efibootmgr -c -d '${DISK}' -p '${PART}' -L "'${LABEL}'" -l '${LOADER}' -u "root='${ROOT}' ro '"${OPTIONALPARAMS[*]}"' initrd=\initramfs-linux.img"'
				break;;

			2)	printf "%s" "--label "; read LABEL
				printf "\n%s\n" "Changed label name to ${LABEL}."
				sleep 1
				efibootmgr -c -q -d ${DISK} -p ${PART} -L "${LABEL}" -l ${LOADER} -u 'root='${ROOT}' ro '"${OPTIONALPARAMS[*]}"' initrd=\initramfs-linux.img'
				printf "\n%s\n" "Created entry with the following command:"
				printf "\n%s" 'efibootmgr -c -d '${DISK}' -p '${PART}' -L "'${LABEL}'" -l '${LOADER}' -u "root='${ROOT}' ro '"${OPTIONALPARAMS[*]}"' initrd=\initramfs-linux.img"'
				break;;
		esac
	done
else
	sleep 1
	efibootmgr -c -q -d ${DISK} -p ${PART} -L "${LABEL}" -l ${LOADER} -u 'root='${ROOT}' ro '"${OPTIONALPARAMS[*]}"' initrd=\initramfs-linux.img'
	printf "\n%s\n" "Created entry with the following command:"
	printf "\n%s" 'efibootmgr -c -d '${DISK}' -p '${PART}' -L "'${LABEL}'" -l '${LOADER}' -u "root='${ROOT}' ro '"${OPTIONALPARAMS[*]}"' initrd=\initramfs-linux.img"'
fi

printf "\n\nWould you like to see a verbose output of efibootmgr? [y/N]: "
read -r DEBUGCHOICE
if [[ ${DEBUGCHOICE} == "y" ]]; then
	efibootmgr -v
fi
Findings, bugs and improvements are welcome. Feel free to post here.
(The revision case block is very ugly, maybe someone has an idea how to DRY there...)