Hello Kathleen--
I don't really have much to add to the comments that you originally posted, and Sharon's confirmation of those. You both have pretty well identified the prescribed sequence of the proper set-up process for your RV.
I concur that I ALWAYS deploy the leveler's before extending the slide, and I do think that can be important, especially in some circumstances. On my 2019, with the Model 725 automatic leveling system, the system will function with or without the engine running--although as with all HWH systems, the parking brake MUST be set. It IS important, I think to have some source of power (other than just batteries) whenever operating a higher-current-draw system (such as he levelers or slide room). That supply can be from the generator, being plugged in to shore power, or (at least in my case) from having the coach engine running. Fully charged house batteries should certainly provide adequate system voltage on their own to operate those systems, but there is no sense in stressing things when you can easily provide auxiliary voltage from an outside source.
As stated, the slide should ALWAYS extend or retract fully (not partially) every movement (in or out), and allowing the slide motors a few seconds to synchronize at the end of each movement before you release the switch will help prevent issues.
I rarely use my awning, so I cannot comment on the parking brake question--I just don't know. The ignition safety feature is logical to prevent awning damage--but it's a good practice NOT to leave the ignition key in the ignition once the coach is parked and set up anyway. I always pull my key and store is in a dash cup holder until I'm ready to get back on the road. As Sharon says, having a regular sequence that you follow each time you stop overnight or for a stay will help ensure everything get addressed and nothing is overlooked.
Mike