While what I can see of your garden looks lovely, there insufficient photos illustrating the issues to even begin to make suggestions. What would likely serve you the best is hiring a designer for at least an onsite consultation. I'm not sure suggestions from an online gardening community are going to provide the best results. This is really a hands/eyes-on situation.

I tried a couple of so-called "designers" and , unfortunately, they were probably no more trained in landscape design that I am. Here are some pics ....just hoping someone used handrailing to access hillside (we are pretty handy so we would be DIY)

This is the lowest point on the east end of the hill (the retaining wall is only 16" tall) and the wall encompasses our patio

this is the west end of the hill....no large retaining wall (bordering hill (right of the tree in the forefront) owned by ODOT ) and, as you can see, I am planting on it.

You could do a series of "stepping stones" which are pegged to the ground by being affixed to the top of posts. The pegging is what makes them stay in place. I'm imagining something like a 3' or 4' treated fence post capped with concrete. I think it would be relatively easy to install the posts in the layout you wished (they could be straight path or staggered) and cast a concrete top in place using a cylindrical form (such as a 5-gallon plastic bucket.)

You've probably done lots of searching yourself, but I have this saved on Pinterest when I was looking for ideas for myself. So many great DIY ideas!

https://www.pinterest.com/pin/294704369352926699/?lp=true

eta: I thought this was especially clever: