Ok - so I’ve noticed a quirk which might be a bug.
I still had some empty bars and rests missing - I found the culprit was rests that had the ‘ends voice’ or ‘starts voice’ property attached. However when I filter rests the option doesn’t appear.
I did some testing and as it turns out the option disappears when more than one bar-rest is selected. Smaller rests can be selected all together and retain their property dialog - it only disappears when a bar rest is added to any selection.