Copying and pasting a node/several nodes (CMD+C, CMD+V) acts as if you pasted twice, resulting in a duplicate set of nodes directly beneath the first set of pasted nodes. If you don’t know about this bug (or just don’t move the top layer of nodes), it can cause serious problems.
Navigating the “search menu” via keyboard arrow keys causes Unity to make an obnoxious beep noise. It’s the noise you get when an asset doesn’t properly capture keyboard events, so Unity thinks that no one handled the keyboard event. Navigation still works, it’s just annoying to listen to.