Where are you located (nearest city & state). Is that garden bed irrigated?

I am in northeast and the area above the retainer wall is no being irrigated.

Northeast what?

"Lots of planets have a north"

What do you have there now and how is it performing? I see a bunch of what looks like daylilies a groundcover and some shrubs. What are you not happy about?

Some option

@Celery. Visualization, Rendering images

What are the pink flowers with grassy leaves? I've never seen anything like it in the northeast.

Yeah, been gardening in several eastern states, zones 5-7 for over 60 years, no idea what those pink flowers with grassy leaves could possibly be.

Guessing your area is mostly sunny towards the right, more shade towards left. Is that correct? And what is your zone?

Height in the back to cover the fence.

You have an informal wooded feel about the layout. I'd continue that vibe so this has more of a natural feel rather than rows and geometric formations.

Fill in space with ground cover that has deep roots that prevent erosion.

@ Sigrid I am not a landscaper. It is just an idea or some flowering bushes and plants.. Better way is to go to local nurseries and check what they have for your zone, preferably native plants.

More visual