Basically, I have subscribed to a few addons through the steam workshop in the past, and the other day I subscribed to a few more. When I opened the arma 3 launcher, the list of addons was completely empty. It worked in the past and I had addons in that list that I'd subscribed to, and I'm not sure exactly when it stopped showing any addons there.
I have found that if I unsubscribe and then resubscribe to an addon in the workshop, it will appear in the launcher addon list, but *only* if I do so while the launcher is currently running. If I unsub->resub without the launcher being open, the addons do not appear in the launcher's addon list until I repeat the unsub->resub with the launcher open.