a comments section on each font so you can list compatible fonts, project file names, cost of font etc. Or a link feature so I can create links between fonts that work together. Sometimes fonts come as duos and sets and being able to grab those or be alerted that they are part of a group would be helpful. Also Store, purchase date, designer spaces (in the background would be fine) etc might be nice in case I am asked to produce a license.
MainType cannot edit fonts, and should not. All it can do is tag fonts. You can create your own descriptive tags.
Font families that belong in a group are already associated by family grouping.
You can create groups for your projects, etc. Then you can add fonts to those groups.
what do you mean by groups? tags? interested in how you have organized yours. any tips to keep thousands of fonts straight would be appreciated. So far I have about 20+ tags narrowing things down. Typically each font has 2-4 tags. I understand the other comment about group by families but what I mean is more like creating a way to say one font looks nice paired with another font. Id like to also tag fonts by designer and what store I bought them from. The license types. Any suggestions there? I guess I can max out my tag list but if I am missing any other way to accomplish that i’d like to be pointed in the right direction 
I have my fonts sorted on my hard drive in folders, largely based on the Foundry or Program that they came from. MainType created groups automatically from these folders when I first launched it.
I added another group called “Catalogue” where I keep all fonts that I want to include in my online HTML Font Catalogue, which I export from MainType.
I don’t use Tags much. I use only one that I added for fonts that can be downloaded from my web site.
awesome thanks for the pics. I found the way to add the groups and now I see where that shows up. So I am off and running creating a bunch of folders and filling them with the fonts that coordinate. Now when I look at a font I will know to see if its been popped into any groups and then I can go see what its been paired up with. Fantastic. I also realize now that my “store” issue has been resolved because that is how they are grouped on my drive. So I see that info is there as well, it was just hidden down a bit. And that same window holds the artist info. So check check check. Thanks for pointing me in the right direction! 