Omnioutliner and Smartgroup

I have many oo3 files and I would like to create a smart Group to gather them all, of course I could tag them but is there another way ? I tried sort = other or put for ex oo3 in comment and have the smart Group search for this comment but it does not work
Thanks

I have global smart groups in my global side bar for each of the major file types that I use in databases. i put the smart groups there so I can search for OO3 and other file types no matter where in my databases they might be. So, here is the format I use. I just change the smart group name and the search target for each of these smart groups.

The dot in “.oo3” isn’t essential – “oo3” works too.

Fantastic ! thanks a lot …