On Linux Mint 19.3 Cinnamon with git Geany and plugins I can't reproduce the problems in the original comment.
- double click and right click->open in geany both work - open external doesn't work because the configured application (nautilus) isn't present on my system, but I get a message to that effect, so the menu is working properly
- find in files uses the selected directory, _if_ you select FIF from the FB right click menu, not if you select FIF with the geany menu. That seems correct, plugins can't affect Geany actions.
``` 09:57:39: Geany INFO : Geany 1.36 (git >= 4bceddb4), en_AU.UTF-8 09:57:39: Geany INFO : GTK 3.22.30, GLib 2.56.4 ```