Well--not when LW is running.

Otherwise, there is a chance that Yes, it can be done . . . but is risky. Different versions of LW had ways of storing the incomplete info, and so not worth the chance of messing up the prefs. So, I'd say wait until the downloads are completed before doing the move.

Typically the prefs look for the incomplete folder in the same directory as the saved folder. So, as long as the incomplete folder (and contents) are where they are expected, downloads will resume.