I can filter a folder on multiple groups using the instant filter..
The same pattern matching technique does not seem to be supported in a folder format filter. A single grp:images or grp:movies filter works but when they are combined as shown below, all files are filtered out.
It's a quirk of the way the grp:xxx notation works, and the different results because the filter field uses partial matching (by default, anyway) whereas the Show/Hide filters do not.
When you use the grp:xxx notation, internally this is converted to a traditional wildcard string matching the appropriate file extensions.
For example, grp:images might be converted internally to *.(gif|jpg|bmp|png).
However, if the grp:xxx prefix is immediately preceded by a ( or a | character, the group is simply expanded to a list of file extensions.
For example, b[/b] would be converted internally to b[/b], but the brackets come from those you supplied instead of being added automatically.
In your above example, (grp:images|grp:movies) is becoming something like:
[b](gif|jpg|bmp|png|wmv|avi|mpg)[/b]
This works in the quick filter because of partial matching (which automatically inserts a * at the beginning and end of the pattern), but in the Show Filter it fails.
The solution is to change the string used in the Show Filter; you can either leave out your brackets altogether: