One way of doing this would be to use the “Compilation” tag, and make sure it’s set on those albums that are not complete operas. I’ve just checked my own collection, and Roon made a mistake and set a complete recording of Gotterdammerung as a Compilation, and missed a couple of albums that were in fact compilations, but a few minutes in the Album Editor fixed that for me.
So, complete Operas:
Snippets and highlights:
I should probably add that this isn’t always perfect; the Delius, for example, is an 18-CD box set (i.e. clearly a compilation), but which contains recordings of two complete operas, A Village Romeo and Juliet, and Koanga. Then it’s down to your individual call as to how you want to classify such things in your own collection, and tell Roon appropriately…