Thanks for taking the time to answer Bart
Unbelievable that such an obvious feature isn't available in a mature product like C1??! I tried Format without success like you said.
It usually takes someone to need/test it, and a service request will fix it (assuming it is broken). There is also a possibility that I also used it wrong because I never tried it before.
Chance has it that filtering based on keywords is more popular, because professional users often use the IPTC fields for adding lots of data and keywords. Filtering by added keywords, with the terms you need to find stuff, does work.
Raw conversions also get tagged as "Processed is true | is false", so you can use that to differentiate between Raws and TIF/JPEG/PNG/etc. . Searching for .raf or . cr2, etc. also works.
In addition, if you work in Sessions, the Raw converted output is sent by default to a folder called 'Output' (can be changed by the user). And you can specify in the preferences to even see (or not) non-Raw formats like TIF and JPEG.
But being able to use the search dialog (and Smart collections) would be the easier path forward. Maybe it is mentioned in one of the excellent Tutorials how to do it even more efficiently.
Cheers,
Bart