[nerdponx]

FWIW I've significantly improved my experience by breaking up my notebooks into smaller pieces such that each notebook only does "one thing", while using DVC to run them and keep track of intermediate results. Or in a case where the intermedaite result was itself somewhat "exploratory", having the notebook itself check for the existence of an intermediate result and load it from disk instead of recomputing it.

Execution barriers are a nice idea though. There is/was a Jupyter notebook extension for "initialization cells", but the whole notebook extension ecosystem seems kind of dead and it's unclear if Jupyter Lab will ever have equivalents.