And there you have it, the idea for the next Sue style (or more like the latest to be added to the queue), "Castle Under Siege", a hybrid city/dungeon scale style with siege engines, castle walls in various states of repair mounted and foot soldiers, burning building, dead things (people and animals)

Looks very nice, but since you have gone for a more "expanded" settlement view, instead of a single symbol, maybe that dashed line for the road isn't the best, as it crashes a bit with the rest of the visual. Those dashed lines work best when you keep everything on an "abstract" level (Such as using a single symbol to represent a town).

Man, you're on a rampage today....

Deleting them from the map still shouldn't affect the symbol catalog though. After opening the problematic map, did you try and change symbol catalogs to something else, and then back to the vegetation catalog, using the symbol catalog button in the top toolbars?

As for copying thing to a new map, that is easy. You can either copy everything to the clipboard (Edit -> Copy) [Just keep an eye on the prompt to make sure you complete the command properly] and then paste it into another map, or you can use Draw --> Insert File to insert the old map into a new one.

Whatever you do in Symbol Manager in your map only affects what you see in the symbol catalog window when you use :ICON_DRAWING:. No matter how much you mess around, you should be getting the normal view when opening a symbol catalog, for example by clicking a symbol catalog button.

(Only way to mess with the actual symbol catalogs is to open them up for editing using file -> open as opposed to loading them into the symbol catalog window)