I've used local mapping successfully in the past, although it has been a while since I last made use of it. Although I have gone through the motions it doesn't seem to be working for me.
I've added a folder containing a css file I want to work on and that is showing up in the workspace.
The folder and css file show up fine in the sources panel - see screenshot below:
When I go to 'Map to Network Resource' I can find the relevant css on the server I want to map to.
But nothing seems to happen when I have selected it.
If I go into Settings and check mappings I can see the mapping seems to have been set. But the browser is clearly still working from the network file.

Any thoughts?
Sam