I get the disappointment, but at the same time I cannot envisage a single use case that cannot be addressed by using Roon’s tagging functionality used in conjunction with its bookmarking capability (which is dynamic).
Perhaps what’s missing is a tag name that you could write to outside of Roon knowing Roon would pick it up and automagically add it to its Tags. Implicit would be the need to assign more than one tag to an album so you can slice and dice the lot any which way you like.