[Michael Wörner]

For “Heal” to work, the two events in question need to be selected and not locked and they must be adjacent on the timeline. They must have the same number of takes, all corresponding takes must reference the same media stream, and their take offsets must be so that the second event starts exactly where the first event ends.

All of this will be true right after splitting an event (maybe except for the selection).

If these conditions are fulfilled for at least two events on the timeline, the “Heal” item will be available and clicking it should merge those two events into one.