"Learner Viewable Area" slide view while building courses

For years, I have struggled with working within the viewable area of Storyline slides. I know you can turn on guides, gridlines, ruler, and snap-tos. All of these are helpful, but I would truly love a hard learner view as well. Meaning there is still edges around the slide edges, but there would be a defined edge of the slide to help with what is exactly viewable by the learner. Because once you start adding overhanging gradients, pictures, shapes, etc. it's a little hard to see the exact edges of the slide. 

I've always heard to do a quick "slide preview". But many of my slides have a lot of animations, audio, videos, etc. so doing individual slide preview loading time really adds up. Plus you can't make edits during the preview.

My homemade solution is for seeing just learner view, is making a locked transparent shape with a border. It's like a picture matte that place over the top layer of the slide. But it's out of view for the learner, so I don't have to worry about it being seen by the learner. This is just extremely annoying to work around, so I keep it hidden until I need to really see it.  (see pictures)

My request for Articulate is to create a workable view that is "Learner Viewable Only".  This would give a definite view of where the edge of the slide is while building content. 

I hope this makes sense.