I think the movements you're referring to are for the 3 light engine moves for the 3 (sets of) diesel locos coming off the Southbound (Up) Highlander portions to go to Craigentinny depot for a couple of hours before returning to work the three Northbound (Down) Highlander portions from Waverley after the train splits.
The locos head off in different directions to Craigentiny as the portions are brought in in order (Aberdeen, Fort Bill, Inverness I think usually) with the loco at whatever end it's at after attaching its coaches to what's already in the platform to make up the full train to head South (hauled by the electric that's usually been sat in the bay as 92033 has been today). Hence some of the locos bringing in the North of Edinburgh portions will need to head out of Waverley one way and some the other.
I think there are more paths in than are always used so CS/GBRf have flexibility depending on loco/driver allocations for the various portions each way.
This video (including the description) may give a clearer explanation - note it was ScotRail days so the traction is different, but I believe the shunting manoeuvres are pretty much the same...
https://youtu.be/5rMxkPUu2dY
Someone like Scotrail84 will be able to explain it more clearly/accurately I suspect, but hopefully that makes some sense...?!
The coaches don't go to Craigentinny - they stay in Waverley (with the passengers) during the shunting and then head off either as a single train South (Up Highlander) hauled by the 92 (or 90) or split 3 ways and go North (Down Highlander) with 67 or 73s.
Incidentally the 73s don't work with the 67s (usually at least). The 73s were working with 66s for a bit due to alternator problems but that's pretty much sorted now I think and 66s aren't normally involved these days. The current typical traction in recent weeks is:
Aberdeen - 1x 73/9
Fort Bill - 1x 73/9
Inverness - 1x 67*
*The Inverness in time will be 2x 73/9s, and has been once or twice in recent weeks, however it's currently the DB 67, which is being loaned to GBRf as a "courtesy loco" after 73969 got bashed in a shunting accident at Craigentinny and is out of action at Loughborough getting repaired.