I currently say an item is "blocked" or "unblocked".
How can we unblock X?
What is blocking Y?
We have too many blocking / blocked tasks.
This may work especially well in my field because the term "blocking" means in software development almost what "un-actionable" means in managementese.
Off-topic anecdote: I wondered the same as you, but my motivations were different than yours. I hate management speak for the reason @ghoppe stated - they are often an artificial cluster of meaningless words to pretentiously avoid simplicity (ok I said it much stronger). I will never forget when my non-native English speaking friend laughed when she heard, "So now what you are going to want to do here is X" instead of simply "X". Not management speak, but illustrates what lengths we're willing to take just to use more syllables.
I just realized a very common phrase in the corporate world that could easily be used for what you need: "In X's court"?
Is that task in our court?
Means, "is progress of the task currently our responsibility?". If you answer "no", you don't necessarily imply that it's anyone else's responsibility either. So, it doesn't imply whether it's actionable in general or not, but I think in usage this is a very close fit.