Okay… but this “engraved panel” does not really need some displacement because mainly it does not changes the outline… so you are fine with a normal map to fake the light angles and so get the impression of geometry.
If you really want to make a displacement map then i suggest using a multires modifier because baking a height map with this was support for a long time… baking normal maps is also but height maps is (was?) not so nice… on th eother hand there are multiple solutions to generate a height map from a normal map… with or without blender.
You can even paint a heightmap with any painting app (including blender 
)…
Or make your own setup with camera and approriate depth values to back a deeps maps… like for example this recent “test”: