If so, [this patch](https://gist.github.com/codebrainz/71d761e2cfd7e7519106ce4f731dd5ee) should work, but it doesn't since Geany ignores request to use existing socket file when no filenames are given, so it always opens a new instance. I have no idea where that code is, but something like this should work with the patch if it was fixed:
```bash $ geany -u # or $ geany --socket-file=/what/ever -u ```