Enhancement: Show user what symbols are using a color

[kiwirm]

When deleting a colour with symbols associated with it, the dialog will appear:

The map contains symbols with this color. Deleting it will remove the color from these objects! Do you really want to do that?

Firstly notice the inconsistency between symbols and objects in the dialog text.

Additionally, Mapper provides zero indication of which symbols are going to have colors deleted, which I think is essential information to the user. Why even show me a dialog saying that some symbols are going to be affected, if I have no idea which ones?

One solution to this frustration would be to right click on a symbol with an option "Select all symbols with this color", for example. In my opinion this is the most elegant solution as it is consistent with other options and right click menus within the program and makes intuitive sense.

[dl3sdo]

Indeed, the map rather contains objects and uses symbols.
The map information tool would provide you the option to determine the usage of colors by symbols:
#2018 (comment)

[dl3sdo]

Now as draft pull request #2125

[kiwirm]

That looks good, but I would prefer to have a right-click action additionally.