Driveway / parking space with a garden bed - How should the edging be constructed?

Perfect. That sounds like a good plan. Have fun and good luck. You can then show us a picture or two.

We also did it with a concrete keol. That worked very well. Regarding the bed, you should think about what really needs to go there. For example, a tree or roses need much thicker soil coverage than other plants that have very shallow roots.

….Regarding the bed, you should consider what really belongs there. For example, a tree or roses need much thicker soil volume than other plants that have very shallow roots.

Don't worry about that.. it's amazing how little space plants can manage with. Our roses and our vine, for example, are in a super narrow strip of bed, right next to the garage, and are thriving there :) At our previous house, we had a grapevine in a pot on the terrace, which found its way through a joint into the soil!

In the first picture just to illustrate how narrow the strip is…