<insert usual apology for this being commonly asked, etc. here…>
What’s the best way to get a compositing node setup from one .blend into another? The one way that I found, after a short bit of tinkering, was to append the scene from the outside .blend, but then getting the nodes from one scene to another is problematic. There seems to be no copy/paste function for these. What do you do? (…besides recreating them all - a pain for complex setups.)
Also, is there a way to have multiple noodle setups per scene, with the ability to select the active one?
In your original blend file, make the noodle a Group.
Then in the target file, the Group will be much easier to find when you Append or Import.
There is only one Compositor noodle per Scene. To have like, i dunno, alternates(?) for a single scene, I would just for organization purposes arrange the noodles above one another, like in strips, so that each one goes left to right. By each major branch, I would plop a Time Node set to the frame range that I intend each branch to be used for. On the right side, this Time node feeds a Mix node that ultimately chooses which branch to use as the final feed to the Output Composite node.