How do I temporarily disable Davinci Resolve nodes?
⌘-D will disable the currently selected node.  Resolve really doesn't like to have loose nodes floating around, so either disable them, or delete them.  But since you're talking about creating a new, experimental node structure, what you really want to do is create a new local version.  Right click on the clip thumbnail and select Local versions-> create new version.  This basically creates a copy of your node structure that you can return to whenever you like.  After issuing the command, you'll see that the name of the new version appears under the thumbnail to let you know which one you're working on.  To revert to the original (or select from any number of alternate versions), right click the thumbnail again and choose versionName->Load.