You can plan now, but wait until the windows have been replaced before replanting to avoid damage to the garden.

I would be likely to plant a small ornamental tree about 8’ or so (depending on the tree width when mature ) off the corner of the house and then underplant with smaller shrubs and groundcover to break up the expanse of blank wall. The bed will need to be deeper front to back to do this.

I might also remove the raised bed in front of the stoop to continue the line of shrubs across, choosing taller shrubs for the area with more height below the windows. Plant something low in front of the low window. I think that the rigid lines of the current raised bed will contrast too strongly with sloped left side of the garden. Adding shrubs across the front stoop will camouflage the contrast. Just keep the shrubs across the stoop area no taller than a few inches above the stoop floor.

Thanks @NHBabs

I didn't think about waiting until after the windows. I also didn't ever think about removing the front bed. I just assumed it was there for drainage reasons. It probably isn't though. I actually hate that bed. Maybe if I remove it I can redo the porch too. We were hoping to somehow add a gabled roof to cover the porch.

Have you considered terracing the slope with a retaining wall or two? Maybe some stairs?

I searched "sloped garden" in Houzz landscape photos and came up with a zillion, although most of them are very high-end and probably not what you're looking for. But a quick look showed several that could be simplified and adapted for your home. On Google try "terraced retaining wall" -- look only at images or you'll get a bunch of ads.

Once you have a few ideas, I suggest you find a local landscape designer to give you a simple design with estimated costs. Some full-service nurseries do this type of work. In my experience the plan isn't terrible expensive, but of course the implementation is! You might be able to do the work over time once you have a plan and understand what's involved.