Nested Tags

I'm enjoying Dex but I feel that it is limited in how I can organise my contacts.

For example, I prefer to have Tags, with sub-tags... in a tree format - with infinite sub-tag structures to really drill down.

I work in a very technical industry and those nuances matter.

For example:

Industry: Agriculture -> Sub Industry: Biological Crop Inputs -> Further Sub Industry: Biostimulants

I can't do this in tags at the moment, and groups is limited to one layer of sub-groups...

I can't create this format either with the custom fields sadly.