Possible technique (This is a pain to use but will get you close)
1) Create a plane at a mid-angle to the two adjacent surfaces. Example: If the part bend was 90 degrees, create a new intermediate plane at 45 degrees to one of the side surfaces.
2) Using the new plane, draw a profile of the 'dimple' and extrude it (as a solid rib) across the corner. This is easiest to do when looking at the wire frame of model. Visulizing where to locate the rib is tricky. Don't worry about the rib thickness at this time because you'll adjust for that is steps 3 & 4. Just fill in where material needs to be added.
3) From a side view, you can trim back any excess rib material back to the underside of the base part. The rib stands out pretty clearly now.
4) Next, from the same 'new' plane go in and trim the rib cross-section (and the base material) for the proper material thickness of the detent detail.
5) Finally, round and/or blend any edges that need adjustment.