Is there a way or a mod to highlight all idle workshops? It seems to be somewhat easier than finding out the idler's profession and then finding a vacant workshop for him to use.
It is very annoying to find workshops where repetitive task was by cursor over'ing it.
Using a manager is not always an option as he can not handle multiple w/shops of the same kind doing different tasks in parallel.
The workflow plugin does preserve repetitive tasks, but does not auto resume them, so it's almost the same as finding workshops with no jobs.
Seeing a workshop empty does not indicate idling as the worker can be busy hauling materials.
Best Answer
Unfortunately there is no way to do this right now. First of all the game doesn't really support highlighting for workshops, once you place them they look the same indefinitely. I am familiar with most of the plugins and none of them support this either.
With regards to your idling concerns, I have a suggestion that I use in my fort. I set all my non-critical dwarves to have the stone detailing labor enabled, and designate pretty much everything as smoothable. This is ends up basically replacing idling, since it is a near-infinite task, but it doesn't tend to override other labors. that way your dwarves don't make friends and do something moderately productive instead of idling.