LaunchBar | small Windows freeware program that mimics the behavior

You need to decouple WindowManager from Bar .

If Barneeds to access the window manager functionality. Use an event/delegate and let the window manager subscribe so it can action what ever it needs on Bar. or create an interface that is common between them so you can pass down that contract to bar.

Either way, you will need to refactor this in a way that logical dependent projects only take care of responsibility that makes sense for them at that level.

Think about it, a builder hires a bricklayer. The bricklayer doesn't and shouldn't have any knowledge of the accounting software the builder uses, he just gives back an invoice when the work is done (an event), he doesn't call enter invoice, or pay contractor on the accounts software. The accounts lady does what she needs, and gives a wage to the bricklayer (or what ever).

In short the bricklayer has an event, or they share a predetermined common contract (interface), which is to say, if bar has an IWindowManager interface it can call GetWorkspaces().

Anyway, only you have the ability to logically split this up without circular references, and what makes sense to you