That simplifies filtering alot (didn't notice that dropdown had got a lot of new entries after installing the plugin). However, it didn't help displaying how many items there are in each gallery (as that field is not available in the fieldlist for Column1-4)
I found a manual sollution:
First I found the fieldid for title='_pg_CurrentUploadedItemsCount' in jos_comprofiler_fields (in my case, 73).
Then I added this manually to the end of col1fields in jos_comprofiler_lists (in my case, the value set was '28|*|42|*|41|*|50|*|27|*|73').
Then I, for some reason, had to copy the line 'DEFINE("_pg_CurrentUploadedItemsCount","Current Items");' from the gallery plugin language file into the CB language file.
Now everything works like a charm! (But please show me an easier way of doing all of this, too
)