Just picked up a new 273 toy hauler and forgot to ask how I tell when the fresh water tank is full? My last RV you could pull the couch away and see the water tank when it was full. No idea where the water tank is on this thing to see when it fills or say if I only want to fill 1/2 way.
If your filling it, I just wait until it comes out the overflow, tube under the camper.
If you are at camp and want to see your levels, there is a push button, that will light up a series of indicator lights. You can also check the batter level, Black and Grey tank levels at the same location. usually the control panel is near the entrance, sometimes behind a decorative door. usually the electric awning controls is near it too.
Not sure about your model, but in my current Jayco Eagle and former Keystone Passport, the fill inlet has a small hole beside the inlet hole. When the tank gets close to full the small hole will “spit” water letting me know the tank is full.