I can see where my mistake is. I use the rule on a different device than the one where the corresponding Thing would be present.
On this device I use the Homematic Binding and added a thing.
Maintenance *unfold_less*
### Signalstärke
homematic:HM-Sec-RHS:MEQ0461285:LEQ1253282:0#SIGNAL_STRENGTH*content_copy*
Number
*unfold_more*
### Niedriger Batteriestatus
homematic:HM-Sec-RHS:MEQ0461285:LEQ1253282:0#LOWBAT*content_copy*
Switch
*unfold_more*
Rotary Handle Sensor *unfold_less*
### State
homematic:HM-Sec-RHS:MEQ0461285:LEQ1253282:1#STATE*content_copy*
String
*edit* *unfold_more*
### Niedriger Batteriestatus
homematic:HM-Sec-RHS:MEQ0461285:LEQ1253282:1#LOWBAT*content_copy*
Switch
I’ll have to come up with something else. My devices exchange state and command via MQTT. As you can see here.
The binding was installed on the “server” and the rule was used on the “proxy”.