Finding idle workshops in Dwarf Fortress

Solution 1:

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.