Your jack system should have a "set level" function. You would level manually then "set [the] level" to tell the system, "this is level". It will memorize that setting. I suggest manually leveling with slides out but that depends on your setup habits.

Unless your RV manufacturer specifies putting the slides out before leveling, it is best to level with the slides in and adjust if necessary after they are out. On softer ground or gravel, we often need a bit of adjustment after a few hours of movement in the RV since some of the jack pads will settle. Also, put the slides in before unleveling. We once messed up a slide topper by bringing our large slide in after unleveling.