When joining reels of a feature together say 3/4 reels on a 6000ft spool, what is the process of marking the joins to enable the reels to be broken down again afterwards? Also, I assume the splicing tape is peeled off instead of cutting the splice out so as not to lose any frames. I imagine the process applies to all film gauges when making up a programme or transferring smaller reels on to a larger one. I find it slightly awkward to locate the correct join on the rewind bench when more than one splice is present.

There are a number of ways to mark the join.
For 16mm and 35 one can use a white China graph pencil to mark the point of the join under the tape,also one can add a very small piece of very thin coloured tape under the join.Super 8 is I think best served to be marked with the pencil as you don’t want a “thick”joint .
Clean off all old tape before a rejoin and make sure the film is clean.
Most have there own personal way to mark to know which is their join is and of course leave one frame on the leader to identify the exact point where which leader goes .
Of course the problem as you say is if there is a lot of splices around where the reel begins and ends .Its really down to you to make the decision unless of course you can find cue dots to give you guidance.
Everyone has their own style of making up and breaking down film and I’m sure other members can add their different ways,evenness down to those stories of wrong film on wrong leaders etc.Not that it ever happens!!📽📽

I suggest that a CIR splicer is used with the tape on one side only. This makers it easier to remove when breaking down.
To later find the join, use a black fibre pen to mark an "X" over the tape.
From my cinema days when we received a new print which had the leader intact and no join into the picture, we always cut off the leader with one picture frame remaining. The same on the tail with one frame left on the tail. This enabled us to be absolutely sure that the correct leader and tail were reattached to the correct same part. To find the join we applied white Tipp-Ex (typist's correcting fluid) on the perforations for a short distance either side of the join.

Thanks for the info! Now I can press on.