Hi, are you using greyscale bitmaps ("bumpmaps"), or rgb normal maps?
For normal maps the workflow should be:
bumpmapping > corona normal shader > bitmap
They should be displayed in material editor and in render.
I can confirm that the strength spinner does not seem to work in bumpmapping tab when using normal maps.
In 3ds Max there is a strength spinner in Corona normal shader, so adding it should probably fix the issue...
I had no problems with greyscale maps. They seem to work straightforwardly.