Something that is pretty common in graphics editing software (as layer locking), and what I'd love to see being implemented in OpenMPT too at some point - flagging patterns as locked, to disable any editing on them, and indicating this state in the order list/treeview by displaying small icon (padlock, etc).

Summary pretty much describes it sufficiently enough, I also attached a quick mockup of how things could look like.

I know there is a globally working edit/recording switch already, but for some people, (me included) selective locking would be better.
The only important thing to consider I can think of is whether to lock all instances of the same pattern, or to treat them completely independently, but that's something that could be set manually by user to their own liking IMO.

I would be happy with any of these ways to do this.