As an example, if SLADE is already open with a PK3 file, and then you open a second PK3 file from Windows Explorer with SLADE, a new instance/window of SLADE will open, resulting in two active SLADE ...
Source files from my pk3 game Now you can see all shitty code and etc. or you have a problem with a code,and my shit code can help someone lol Windows or linex,macOS ...