For the new feature in 6.8 to persist permission choices, it looks like it picks up the data path too early to let us change it later with QWebEngineProfile.setPersistentStoragePath().

The permission manager sets the data path when its initialized. 
It's initialized lazily from the getter in ProfileQt.
That getter is called from the ProfileAdater initializer, which is too early for callers to have changed the persistent storage path.

It looks like calling ProfileAdapter::setStorageName() would cause the permission manager to get re-initialized with the new storage path (and it looks like that's what QQuickWebEngineProfile does), but that's not part of the QWebEngineProfile API. I tried to find other ways to change where permissions are stored post-initialization but couldn't see anything.

We support users running multiple browser instances at a time with different profiles with their data isolated. We are using
setCachePath() and setPersistentStoragePath() on QWebEngineProfile to achieve that. This change means that users won't be prompted for feature permissions the first time they visit a site in a new profile, if they've visited that site before in a different profile.