I want to search for
*.gif *.bmp *.jpg
OK none of those worked. ; , space, what do I separate the three file extensions with?
Is there a shortcut if I frequently search for .gif;.bmp;*.jpg, but don't want to type all that every time? Can I somehow create an alias?
If you're using the basic Find dialog box, you can configure it like the screen grab below.
If you're creating a button, you can use the following command in the button to filter for several image types.
Set SHOWFILTERFILENAME *(bmp|cr2|dng|eps|gif|jpg|jpeg|orf|png|psd|thm|tif|wmv)
Or use a File Type Group.
To add to what Jon said, you can grp:Images as the "Name matching" pattern (as well as in filter boxes etc.) to match all extensions in the Images file type group.