we are testing this very nice software in my experiment at CERN called CMS.
Many people are asking me to understand if there is any way to increase the sub-category dept level from 2 to 3 or 4.
In our field having a category + 1 level of sub-category is not enough.
There is a hidden max_category_nesting site setting that you can play with if you’re self-hosted (and you might be able to use if you’re hosted and ask nicely, but I really don’t know). You’d need to set it with an ENV variable in your app.yml or at the rails console. I’m pretty sure that it’s largely unsupported (my guess is that it likely works because enterprise customers are using it, but you’ll probably be on your own to figure it out in the near term), so using tags is almost certainly the better approach.