You found a pretty old part of the code my friend. It looks like that setting got deprecated way back in the day. I can only trace it back to v4.7 (roughly around 2007) and it could have been abandoned prior to that for all I know.
As for the Manage module, my guess is that it was just never necessary to have the extra row taking up space at the top of the module. I think people don't use it that often (with bridges especially) and when they do, having the bridge show in All Modules is sufficient.
The best thing about a boolean is even if you are wrong, you are only off by a bit.
Hmp. I just installed DrTech's plugin and thought the best place for the button would be on the Manage Module. No need to have it anywhere else. Ended up putting it on the Acct Module, even though I don't think it belongs there.
Couldn't download the plugin for 13.2, so I installed the plugin for 13.1
It worked except every time I opened the chart module OD crashed.
Another interesting finding was that installing it on one workstation (Program Files\Opendental) enabled it on all workstations, even though the .dll was only on the one workstation.