@b4n I added this feature to the plugin that other LSP clients implement as well (not tested much yet):
https://github.com/techee/geany-lsp/blob/c56de66cecf4dff2c1b1a98ea37b22bd2af...
This should essentially allow automatic opening/closing of multiple projects even if no Geany project is open and at least partially fix the problem you had when opening random files.