As an administrator, I cannot use the "Create form" button on https://(hostname)/transactions/editengine/maniphest.task/page -- it reports "You do not have permission to create these objects." I cannot edit existing forms; it reports "You do not have access to any forms which are enabled and marked as edit forms." I can, however, modify the order in which the existing forms are presented.
I cannot find the location to change the access control to allow me to edit the forms. https://(hostname)/applications/view/PhabricatorManiphestApplication/ has permissions all set to "All users" or "Administrators", so I satisfy all of those. https://(hostname)/applications/view/PhabricatorTransactionsApplication/ similarly.
A fresh Phabricator instance appears to grant me the ability to create new forms, so this is a permission which has degraded during an upgrade, or is otherwise squirrelled away someplace I do not know to look.
Phabricator version is 216f6be11ece53cb1daafc8fff636dbdb0d7ef3d with likely irrelevant modifications.
cc @ahoffer2