As I only will use Roon ARC in “offline” mode, I wanted to see only my Roon local files in Roon ARC, but I do not see this option to filter the library?
95% of my library is from Tidal so just browsing would not make much sense, but I still want to download some to try out the app, even though it’s sort of useless without Tidal offline content.
I am having the same problem. I am using ARC on an iPhone and via wifi. I want to be able to only see my local files that are in my ROON Nucleus+. But I see everything in my library, including the ones I stream from Qobuz and Tidal.
You could create a tag in Roon called “Local” and apply it to all your local albums or tracks. Then use that with Roon ARC.
Or, you could use Focus in Roon to select Tidal and Qobuz albums, then apply a tag to them called “Not Local” or whatever. Then in Roon ARC use that tag and click twice to get the inverse which would be all your local albums.
Yes, you’re right in that I could do that to “fix” the problem, and thanks for the tip, but I doesn’t mean that it’s still a flaw in the app that it’s not possible to do natively. Do I have to tag the team to be sure they read this? Sorry @brian, you’re they only one I remember the name of 
It’s a current oversight due to lack of focus options in v1 and lack of bookmarks. I am sure they will be looking to add more options as it develops. The tag system is an easy and quick way to do this but does require you to manually update and tag each new album/s you add. Here bookmarks would be so much better as they update based on the focus used to sort them for all new additions.