If I didn't use a bevel modifier but I beveled directly the shape edge of the mesh with Ctrl+b, I usually use this procedure:
- In edit mode, set the Pivot to Active element;
- select all edges I have to de-bevel and for last one I select the one aligned to the original position that I will use as reference;
- scale the selection to 0 on the needed axis only, to align all beveled edges to the reference edge;
- repeat the same operation with the other side to de-bevel changing the last selected edge and axis accordingly, as needed;
- Remove double vertexes.
This works on one "beveled corner" at once and if the edges to be de-beveled are aligned or orthogonal to axis. If they aren't there is the need to set a different xyz ref system to match local edges alignment.
If you wish, see the following video to see the tutorial I made: