View List with distinct term listing of multiple nodes

I have a map where multiple nodes are shown as marker (filtered by terms). Now I would like to add a caption (block) which explains the (filtered) marker. The map may contain several results with the same marker.

So the map shows filtered by TERM 1 and TERM 2 shows following results:
NODE 1 (as it uses TERM 1)
NODE 2 (as it uses TERM 1)
NODE 3 (as it uses TERM 1)
NODE 4 (as it uses TERM 2)
NODE 5 (as it uses TERM 2)

In the caption (block) I would only like to show the distinct result:
TERM 1 (the marker image + name)
TERM 2 (the marker image + name)

FILTER > TERM 1
The desired result would be ONE result:
TERM 1 (image of that term)

But it does not matter what I tried (for 2 days), the result is always:
TERM 1 (of NODE 1)
TERM 1 (of NODE 2)
TERM 1 (of NODE 3)
TERM 2 (of NODE 4)
TERM 2 (of NODE 5)

Please give me a hint to understand why I cannot manage it.

Kind regards,
Benjamin