I tried to create a button that extracts an archive and then deletes it.
But I can't get it to disable, unless an archive is selected.
@disablenosel:type=grp:Archives
Copy EXTRACT=sub HERE
Delete
If I add @disablenosel:type=grp:Archives, it stays always disabled.
I also tried type=*.zip.
Downloaded the button from here to make sure it's not just my button not working:
That's odd. Button looks good and works fine here 
Adding the info from this thread I'd say there's something wrong with your setup. Not sure what that could be, unfortunately.
Which version of Opus are you using?
Is the button enabled and working to extract the archive if you remove the @disablenosel line? It might be disabling for another reason (e.g. the type of folder you're in).
For the grp:Archives wildcard, it could go wrong if .zip isn't in the Archives file type group:
If Preferences / Miscellaneous / Advanced [Information Display]: multipart_extensions has been changed, that could also affect things.
Ah found it, in German the group is called Archive, not Archives. It works with Archive.
That explains it! Although type=*.zip should still have worked.
It does now, I guess I made another mistake there.
