We don't get the true wire by wire schematicson the Rv after 2010, so without knowing which model of 2021 Navion you have it is a bit of guess where is best to find power. A lot will depend on when you want this power hot and where you want it, high/ low, etc.
For low power and when the headlights are on, just tapping into one of the taillights, sounds easy. If you want it more full time hot, looking at the starter solenoid for the generator will get a good solid connection with much higher amp capacity.
A trailer connection is often a good place to tie in for power for a light, etc. but I see no connector on your RV.
Left side rear storage seems to have several items which might have power at the right time. I see several switches and a light. I would not want to try the water pump switch as it is likely to have several switches on the pump, making it hard to get one that is full time.
One way to sort where a wire goes and what it does is the code that is stamped on each wire.
Once you have the code in mind, you can use this chart for decode to find if it goes to power and under what conditions.
https://www.winnebago.com/Files/File...ical_guide.pdf