I think I figured out the problem, and it's super wierd. This only happens when "Live Save" is enabled. And it ONLY appears to affect the Color page.
In the following screencapture, you can see that disabling Live Save causes the contextual menu to stay active, as is normally expected.
However, when you enable Live Save again after having disabled it, and you open the contextual menu again, it will continue to stay open. However,
once you force a project Save, the menu starts closing by itself again!
This occurs in every contextual menu on the Color page (and not just the Keyframes panel, as I originally posted). It does not appear to affect the Edit page, however.
Resolve Studio 18.0.2 / Decklink Mini Monitor / 14" 2021 Macbook Pro Max (macOS 12.5.1, M1 Max) / 32GB RAM