the GOG shortcuts usually have a -c "exit" in them, remove that.
Otherwise, please give more details on how you "added" the editors.

Thank you for your reply.

I have attached the full config file from the GOG xcomapoc folder below to show how I have added the two editors:

[ipx]
# ipx -- Enable ipx over UDP/IP emulation.
ipx=false

[autoexec]
# Lines in this section will be run at startup.
@echo off
mount C ".."
mount C "..\cloud_saves" -t overlay
imgmount D "..\CD\xcom.cue" -t iso
c:
goto launcher

:launcher
cls
ECHO [1;33m[42mÉÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ»
ECHO º ------------------------------------------ º
ECHO º X-COM: Apocalypse Launcher º
ECHO º ------------------------------------------ º
ECHO º 1) X-COM: Apocalypse º
ECHO º 2) Game DOS Settings º
ECHO º 3) Xed º
ECHO º 4) Ovrkill º
ECHO º ------------------------------------------ º
ECHO º 5) exit program º
ECHO º ------------------------------------------ º
ECHO ÈÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍͼ[0m

choice /c1234 /s Which program do you want to run? [1-5]: /n
if errorlevel 5 goto exit
if errorlevel 4 goto ovrkill
if errorlevel 3 goto xed
if errorlevel 2 goto setup
if errorlevel 1 goto game

:game
cls
xcomapoc.exe SKIP
goto exit

:setup
cls
setup.exe
goto launcher

:xed
cls
xed.exe

:ovrkill
cls
overkill.exe

:exit
exit

Is that enough info or should I add more ?

When you press [3], the menu goes to the xed label. For some reason the xed program fails to start, then the menu execution continues to the ovrkill label. And apparantly Overkill fails to start as well. Finally the execution continues to the exit label and DOSBox quits.

You probably want to add goto launcher at the end of the xed and ovrkill labels (menu execution returns to the launcher label).

You should debug the menu yourself:
Do the editors work if you launch them directly without the menu?
Add a pause command in the script after xed.exe so you can see if the program prints some error message (and the same for overkill.exe).

Thank you for the very helpful reply 😀

By using the suggested pause command, i discovered that Xed fails to start because it requires the game to be installed with the full install option and the GOG version of the game only uses the minimal install option.

The overkill editor now works perfectly.

So far so good!

One full install of the game later and Xed now works perfectly as well.

Problem is now solved.

Thank you to both Qbix and zirkoni for your quick replies and great help.