Run it from command line not by clicking it.
Yes, you can use ArchiveTool.exe (from command line) to unpack and pack .arz files (the program provided by Crate).
Also I think there are some other user tools on the forum. Maybe GUI (un)packing program as well IIRC.
In my opinion AssetManager is the best and easiest to use though. “Making a mod” is basically changing and packing files really.
If you meant that you don’t want to run your mod in-game in a modded game but normal campaign,
I like this method of running with your modified database.arz in Main Campaign (see installation): [MOD] Grim Dawn Lazy Parallel Universe | QoL hard-mod for 1.1.9.3