Answer:
If you simply select an element in RFEM 6 by clicking it, this appears in the selection or the selection list. If you want to deselect this object, press the [Shift] key. The "-" symbol appears on the screen, which means you are in the mode for deselecting objects that have already been selected (for example, boundary lines).
At this point, the program behavior has been adjusted slightly compared to RFEM 5 to avoid accidentally deselecting objects.
