Adding 120vAC outlet to 2018 320s/cs

ObizzyB said:
. . . 2018 320s/cs I would like to install an outlet by my interior front cabinet top to plug in a small ceramic heater to jump start the Alde.

I found this picture of a 2018 320CSS that show outlet by the floor. I'd think that would be an option to plug in a heater. If your set on wiring one up front, I installed an outlet on the wall between the bath and the cabinets. You don't have the sink or power for the refrigerator there, but fishing a wire under the the shower pan might be an option for you. It enters into the compartment behind the toilet where the water pump is located.

The advantages of the simplest approach not withstanding, if you want to avoid tripping over an extension cord, or otherwise find the convenience of having an outlet near the front counter compelling, then I would see no reason not to add one, provided the installer is somewhat handy & has a basic knowledge of household wiring.  Of course, it would require cutting and/or drilling a hole in the wall and adding an outlet box & switch.  Since there is a double wall in this area, it might be easier to use a surface mounted and/or low profile outlet box, or relocate any existing shallow display panel if needed to make room.
In any case, I've located the images below to illustrate the route one might take and the possible structural features in the area..
I assume this is what your wet bath looks like, @ObizzyB ?..

The dotted line represents the route for a power line from under the driver side bench seat, under the shower, behind the toilet wall, and to the wall at the cabinet.
And another floorplan view..

And the green box below would be the target area for mounting an outlet..

Below is a shot of the area under our driver side bench seat near the front of the wheel well.  Circled in green are the AC cables running from the converter area to the raceway that goes under the shower floor pan and into the space behind the toilet wall..

You may be able to wire a new 120V cable from the existing GFCI outlet in this area to extend power (& protection) to the new outlet.
Next below is the view inside the wall where the outlet would be mounted & the route for the cable. 

As mentioned, there is a double wall in this area left of the cabinet, with only about an inch of space inbetween.  If one layer is already cut out, as shown, then you may be able to use that space for an outlet box, but this may require relocating an existing display, if possible. 
Otherwise, a shallow surface mounted outlet box is another option, which would probably be easier & may only require drilling a single 3/4" hole.
For me, this would be a fairly easy project, but it would require having the right power tools, like a drill, at minimum, and possibly a reciprocating/scroll saw or a plunge cutter tool if you recess the outlet box into the wall.
The simplest approach would only require drilling one hole, then installing a surface mounted outlet box.

@ObizzyB The wire path and notes by @BrianZ are excellent. The round outlet I posted in my second picture above was a easy install and the USB ports are a plus. It helped that I already had a 2-3/8" hole saw from a previous project. The round hole was much easier than trying to make a rectangular hole for a standard outlet in that tight location and you a flush mount.

ObizzyB said:
. . . now have a short term fix and a long term (permanent) plan moving forward.🥰

@AnOldUR, nice little round outlet you installed there.  Is that a swiveling cover on it?  If so, great choice for that location where you have a sink.  I've had standard USB ports fail, so I'd try to avoid having a uniquely designed one tied in with an AC outlet where you'd need to replace both if one failed, assuming it was still available.

BrianZ said:

One way or another, it's a doable project.

For @ObizzyB my thought was that the lower location would be an easier install and eliminate the dangling cord that you get when plugging in appliances under the upper cabinet. We have an outlet located up there and it's awkward to have cords dangling over the sink. In my case adding the round receptacle was a way to have separate outlets fed by an inverter and shore power. There are a lot of different configurations and sizes of these round outlets to choose from. 

My 2018 320CS-S has an outlet under the Jensen head where the circle is in the last picture.