UI improvement for "delete map marker"

Delete functionality of map markers supports a single marker or a range of markers. When a delete operation is started (r click on first marker) there is no indication that a second r click on any marker will delete the range.
This may confuse the user and delete a big section of the track.

Possible solutions:

• Show a delete operation UI element
• Prompt for confirmation before deleting more that 1 marker
• Prevent adding map elements while in delete mode