I never worried about starting the RV plugged in or not, generator running or not.
I think that some people have a 'theory' that it is dangerous, while reality is that the design protects us from anything going wrong.
The generator can be run safely while plugged into a 120 volt outlet. There is a safety device to prevent any danger from this.
You can start the engine or generator while plugged in or not.
You really do not save all that much power by leaving the RV plugged in while putting in or out the slides. While the motor might draw as many as 65 amps, this is less than 1 minute, so only 1 amp hour. .. . .
That is the same amount of power consumed by a light bulb over 1 hour.
Same with the water pump, it will consume 7.5 amps per hour. However in that hour, it will also pump 2 GPM or 120 gallons. So you can empty the water tank with only about 5 amp hours of power, really in-significant.
Have fun camping!
Fred.
