Alright, I upgraded to macOS 13 so I'm able to reproduce the issue. I've rebuilt Geany with the latest GTK version and Geany version from git master which can be downloaded here:

https://download.geany.org/snapshots/geany-1.38_osx_arm64.dmg

(The latest GTK seems to improve rendering performance so scrolling seems to be much faster plus there are some minor goodies in Geany so I recommend trying this version.)

First I thought this fixed the problem because when installed, launching the script worked. But once I uploaded the installer to the Geany site and then installed the downloaded version of the installer, it stopped working again. I think this is some sort of security protection to avoid executing some random scripts from the Internet using the built-in terminal.

Then I found this article

https://stackoverflow.com/questions/74187734/launchpackager-command-can-t-be...

with a workaround - one has to use a different terminal application for execution. When you use e.g. iTerm and in Geany under `Edit->Settings->Tools` set `open -a iTerm %c` as the terminal command, iTerm launches without any problems and performs the execute command.