It is far easier to write an action which operates on a single album as there are lots of assumptions which can be made. Personally I always tag one album at a time....or I run the batch processor which walks my collection which is nicely organized as one album per folder 🙂

However, that being said I constantly have to write actions which might potentially have more than one album to work with. Typically I create a list which has albums as keys and the per key value is whatever I'm interested in.

Take a look at the 'Move Creating Disc Subfolders' action on the Resources page (you can easily get there from the Yate Help menu). In there I accumulate the list of albums. This thing does something similar to what you are asking about and as it's a sample action it is documented.

The basic problem is that actions are easier when all tracks are equal. Being in the same album certainly helps. If you have multiple albums, you have to manually accumulate and segregate the information so that you can effectively loop over whatever you're interested in, much as you would in any programming environment.