Keeping the data folder on another drive is no problem, CC3+ is designed to allow that, just select the location from the CC3+ installer, and it will set up correctly for that. The data folder can grow pretty big, so not everyone will have space on their system drive for it. Just remember where you placed it.

You only risk items not found if something isn't done correctly. For example, someone may have manually imported official artwork into their map using the absolute path of their data folder, instead of the more appropriate relative path. Using a relative path means it is relative to the data folder location, and will work no matter where it is placed, which is the way all official ProFantasy resources is set up.

My data folder is ~50 GB.

This forum has the ability to embed CC3+ buttons in posts, which can be a great visual aid when explaining something to people. There are two versions, image with text (ex: :CC2MCHANGE:), and just the image (ex: |CC2CO|)

Adding these into a post is just a matter of taking the CC3+ button image identifier and putting it between two colons or two vertical bars, like this:

:PERIBOX: ⇒ :PERIBOX:

|GLOBE| ⇒ |GLOBE|

Note that this will just show as the code when you are editing the post, you won't see the actual button until you actually post your comment.

Do you have the 2012 annual? Issue 68 has a bit more on these commands, including using them in a tutorial.

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)