Agree, being able to select individual MyTags would be so helpful. I find the current two options to be either too broad or too restrictive to be useful.
I use MyTags for sub genres e.g. the main Genre in my files is Techno, then I use MyTags for Detroit Techno, Acid Techno etc. So I want to setup a related tracks critera of 'BPM & Detroit Techno'