Consolidate the Categories in the Tree View

Currently if you switch the tree view to “Categories” you see the same levels repeated for every model that uses it. Users wanting to control view by category don’t want to have to pick and manage multiple instances of the same level. When wanting to control categories at the model level the Model tree is more useful. This came up when a project had a hundred files with common levels.

Maybe show a single line for each category then allow drill down to see what models use it.