You can search by metadata in Panel, you just need to specify the parameter in the search field. It's formatted as [<Field>]=[<Search Value>]. For example: [File Type]=[flac] or [Genre]=[Classical] [File Type]=[flac].
I think it is great that JRiver provides the technical capability to use a sophisticated search mechanism in Panel... However, this is why people keep on commenting on the UI of JRiver products.
I mean, really? A user has to memorise all the field names, and all the values set for those fields, to do even a relatively simple search in Panel? With no field name or value lookups, no obvious indication in the UI that this sort of search is possible, and no way to set up a search and save it, do you really expect people to use this search capability?
And now that JRiver for Android uses Panel as its UI, the user has to key in that search expression on an Android device, probably a phone?!
About 2% of all users will even know that functionality exists. Of that 2%, about 1% will use the capability. So 0.02% of the user base, or about two people, whichever is the lesser.
If I knew about this capability, I had forgotten. I've complained about the lack of Context in the Panel search functionality before, and I don't think anyone has ever mentioned searching using expressions. Maybe I just forgot this information, because I decided it was all but unusable.
Panel has been around for a long time now. It should be entering maturity. There should be an assisted search capability built into it, that allows selection of multiple search terms, and values available within those terms.
Come on JRiver. I know Cloudplay may be fun, but finish the job with JRiver for Android and Panel. Make them best of breed applications. Please.