Howto set source and target in element template

I think you would need to do two steps…

Input Variable (Formula to Execute): Formel from first example, or “VBEZ*12/100” from second
Output Variable (Variable to Set): BBRV from first example, or ZVBEZJ from second

Then your template would need to call an evaluate on the Input Variable as part of your worker/function.

In theory, the resulting code would be more like:

        <zeebe:ioMapping>
          <zeebe:input source="=84600" target="temporaryVariable" />
          <zeebe:output source="temporaryVariable" target="BBRV" />
        </zeebe:ioMapping>