I used to use Mac's FontBook. Eventually, I got enough font issues that I got Suitcase. I still had conflicts, but it was easier to manage them. But, I've never been 100% satisfied.
Now that Adobe is Auto-Activating fonts, I wonder if I "need" Suitcase? Is it still going to make my life easier? On top of this is purging 7000+ PS fonts from my ecosystem now that they won't be supported. So, less fonts to deal with.
No programs seem to enable me to hide/remove the long list of non-english-language and other unused fonts anyway.
I used Extensis Suitcase for years but got tired of buying updates and kept having issues. One time all my custom categories disappeared. 8,000 fonts separated into different categories (horror, athletic, headline, fun, fancy, scritpy, etc...) was gone. Yet I was still hesitant to let it go, but once I did, I never looked back. I do miss the feature of creating your own categories, but fat lot of good it did when I lost them. I think it was a better company when they were a local start-up (Portland, OR), once bought out it started losing me. Hope this helps.
P.S. I am however having several font issues exporting from InDesign to an epub format. I wonder if Suitcase would be helpful in this.
Are you using any kind of font management now? I am tempted to just go back to Font Book.
Extensis does handle Google Fonts now. That is pretty nice.
I can't give any info on the epub export as I never do that. What problem are you having? Maybe I can to a test for you while running Extensis.
Sorry about losing all your catagories. I hate it when you spend the time to do something like that and it just gets wiped out. Sadness.