Mark dead code as dead. When you want to create some new thing to fiddle with, use one of the many dead code nodes. When you roll it into production, mark the node as dead again.

We shouldn't reuse node IDs. There are places that assume that node creation age is monotonic with node ID. It isn't like we've got so many defunct node IDs (even with the huge number of bogus scratchpads snafu) that reusing them will make much difference as to when node IDs won't fit in 4 bytes any more (and the DB can support larger node IDs than that).

If there are too many dead code nodes marked as dead (I tend to rename them and empty them so they are very obviously dead and also don't do anything), then nuke them (they aren't public nodes so nuking them *eventually* isn't a big problem for me).