[REQUEST] Organize custom structures into groups/folders

[carolinerosin]

Is your feature request related to a problem? Please describe.
Custom structures can quickly get messy, would be nice to be able to create "folders" organize them.

Describe the solution you'd like
User should be able to create "folders" to organize his structures. A folder has a name and maybe a text description ?
Not sure if we want nested folders as well ? Would probably nice to have (because I fear that after a while we will have the "too many folders" problem.

Describe alternatives you've considered
no alternative, I just have to scroll down and look for the right structure in my list.

Additional context
Example of "structures all over the place"