Robust Customising of Locations

[Jacki3]

Is your feature request related to a problem? Please describe.
We can only edit the variable name and data of the location varibale but we have a list of locations that store extra info such as name colour, icon etc.

Describe the solution you'd like
A way to edit these locations fully which may require rethinking where locations are stored or using them as single objects which can be dragged into the variable slot (like the node groups).

Additional context
We need to first ensure that locations are stored as individual classes rather than being a series of properties stored elsewhere (see issue Location Individual Class #21).