If you browse to any of the items under Library, such as Artists, Albums or Tracks, you used to be able to do it in there. However, I’ve just tried it and it appears the feature has been removed, or I have a bug. Maybe someone else can comment if they’re seeing the behaviour.
There used to be an item called "format’ if memory servces, which you could select MP3, FLAC etc. It was quite good.
Klick on the heart Icon to make it a favorite or on the three dots for more options.
This is a shot into the forest because I don’t have Access to roon atm. But it should work like this or similarly…