Pinning and locking elements
Any object — a frame, a group, a component instance, a plain shape, anything — can be locked directly from its row in the layers panel, keeping it out of the way while you work on everything around it.
Locking
Click the lock icon on an object's row. A locked object stays fully visible on the canvas, but becomes un-clickable: your cursor passes straight through it while you work on everything else, so a finished background frame, a group you're done adjusting, or a component instance you don't want to accidentally disturb never gets selected, dragged, or reparented into by mistake.
This isn't limited to single clicks, either: a locked object is skipped by marquee selection too. Drag a selection box across the canvas that happens to cover a locked shape along with several unlocked ones, and only the unlocked shapes get picked up; the locked one is excluded from the selection entirely, exactly as if it weren't there for the purposes of that gesture.
Locking cascades to children. Lock a frame or a group, and everything inside it becomes effectively locked too, not just the container's own outer boundary. A locked frame protects its entire contents from accidental interaction on the canvas. You don't need to separately lock each object inside it one at a time for the lock to mean something.
Why the layers panel is the one exception. You can still select a locked object directly from its row in the tree at any time, even though it's inert on the canvas; this is deliberate, not an inconsistency. If the layers panel respected the lock the same way the canvas does, a locked object could never be selected again to unlock it, since clicking it on the canvas wouldn't work either. The tree stays the one reliable way back in.
Unlocking
Click the same icon again to restore normal interaction. For a locked child inside a locked parent, you'd need to unlock whichever ancestor is actually responsible for the effective lock, since a child's own unlocked state doesn't override a locked parent above it.