I see that it is possible to toggle port forwardings in general:
Now, I want to be able to toggle some further port forwardings on demand (simply for the sake of security - I don’t want to be open all the time). Unfortunately, the new ones don’t show up. Any ideas?
Did you do a reload from the Fritzbox Integration?
Yes - reload, restart router, restart HA
But it doesn’t show up 
Port forward switches
Due to security reasons, AVM implemented the ability to enable/disable a port forward rule only from the host involved in the rule. As a result, this integration will create entities only for rules that have your Home Assistant host as a destination
AVM FRITZ!Box Tools - Home Assistant
if the port is for another IP it will not show up
Damn - but thank you for clarifying 
