This is a screen capture from disk 1 of George Szell: The Concertgebauw Recordings. The album is identified by Roon.
Track 5 registers correctly with Roon. But Tracks 6 to 8 (opus 61) aren’t identified as compositions at all. Even a simple search for “Midsummer” doesn’t find them, so it is not possible to merge compositions. Is it a clue that no conductor is listed? Szell is listed in the credits for all of the tracks. Suggestions?
This composition is often listed including the Overture as Op. 61 or as Ops. 21 & 61. What do you see at tab Edit Album - Multi-Part Composition Grouping? I would expect to be able to solve it there.
I have this recording a single disc and this is what it looks like!
The opus number confusion is real, not just Roon’s. Mendelssohn wrote the overture separately, long before the rest of the music. So there are two opus numbers.
I tried editing my tags to match your listing. But it didn’t display Midsummer Night’s Dream as one composition (or two). Under everything I’ve tried, the Multi-Part Composition grouping gives the correct number of compositions, but doesn’t group tracks 6 to 8.
I think Roon is confused. It doesn’t treat tracks 6 to 8 as separate compositions. But it refuses to display them as a group. Only the overture is listed as a composition under the Mendelssohn composer listing.