Since Forums appear to be a much more independent module than other Dolphin modules, Forum topic subscriptions aren't managed using Manage Subscriptions on the Account page (first attached image). Forum topic subscriptions are managed separately, from the Forum / Subscriptions menu item (second attached image).
If this weren't difficult enough for users, Group Forum topic subscriptions aren't managed in either place, but from the topic itself (third attached image).
There must be reasons for this, but user experience is clearly not one of them. Ideally all subscriptions would be managed in one place, but if this isn't possible, can Group Forum topic subscriptions be added either to Group subscriptions or to Forum topic subscriptions?