mapped via overlay on 
/etc/systemd/system/multi-user.target.wants => 
/usr/lib/systemd/system 

qml-launcher

/etc/systemd/system/multi-user.target.wants

qml-launcher.service 

[Unit]
Description=qml-launcher Service
After=

[Service]
ExecStart=/home/bin/QmlBoot.sh
ExecReload=/bin/kill -HUP $MAINPID

[Install]
WantedBy=multi-user.target

engine.service

root@force:/usr/lib/systemd/system# cat engine.service
[Unit]
Description=Engine
After=

[Service]
Type=forking
ExecStart=/usr/Engine/Scripts/runengine
PIDFile=/tmp/engine.pid
Restart=on-failure
TimeoutStopSec=30
LimitCORE=infinity

[Install]
WantedBy=multi-user.target

inmusic-mpc

root@force:/usr/lib/systemd/system# cat inmusic-mpc.service
[Unit]
Description=InMusic MPC Application
#Wants=az01-script-runner.service
#After=az01-network-midi.service az01-script-runner.service az01-usbsata-fixer.service touch-fw-update.service xmos-update.service

[Service]
ExecStart=/usr/bin/MPC
Restart=on-failure
Type=simple

[Install]
WantedBy=multi-user.target

qmlboot.sh taken from TKG/mockba modified by myself :
#!/bin/sh

mmDev=`amidi -l | grep Private | cut -b5-13`
usrmounted=`mount | grep overlay |grep "/usr" |wc -l`

set_pad() {
        amidi -p $mmDev -S 'f0 47 00 40 65 00 04 '$1' '$2' '$3' '$4' f7'
}


play_back() {
        /usr/bin/ffmpeg -i $1 -pix_fmt bgra -f fbdev /dev/fb0 >/dev/null 2>&1 &
}

# /usr/bin/gadget-uac2
# Part of Mockba Mod, do not modify

echo "Mounting Writable /usr via OverlayFS..."
mkdir -p /tmp/usr
mount
ls /tmp/usr
ls /media/

mount -o loop /media/az01-internal-sd/myusr.img /tmp/usr

if [ $usrmounted -gt 0 ]
then
echo "OVERLAY ALREADY MOUNTED"
else
echo 0
mount -t overlay -o rw,relatime,lowerdir=/tmp/usr:/usr,upperdir=/media/az01-internal/system/usr/overlay,workdir=/media/az01-internal/system/usr/.work overlay /usr
fi

sleep .5
sleep .5
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/qt/lib

udisks --mount /dev/sda1
set_pad 00 00 05 05
sleep .5
set_pad 00 00 20 20
set_pad 01 00 05 05

# Starts MPC
ulimit -S -s 1024
export MALLOC_ARENA_MAX=1
echo 0 > /proc/sys/kernel/randomize_va_space
if test -f /usr/Engine/qml-launcher; then
                export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/qt/lib
                /usr/Engine/qml-launcher
        else
                #/usr/bin/MPC "$@"
                systemctl start inmusic-mpc
        fi

root@force:/usr/share/applications# ls -l
total 8
-rw-r--r--    1 root     root           114 Feb 16  2024 Engine.desktop
-rw-r--r--    1 root     root           110 May  4 21:54 MPC.desktop

root@force:/usr/share/applications# cat Engine.desktop
[Desktop Entry]
Type=Application
Name=Engine
Exec=systemctl start engine.service
Icon=/usr/Engine/Icons/Prime.png

root@force:/usr/share/applications# cat MPC.desktop
[Desktop Entry]
Type=Application
Name=Force
Exec=systemctl start inmusic-mpc
Icon=/usr/Engine/Icons/Force.png