Group & copy a block in custom workouts

I’m setting up some custom workouts; these have warm-up, then 3 phases that repeat a few times (say 4 to 6) then cool down. Itwould be very helpful if there was some way to create the 3 phases (easy enough right now) then be able to group them into a block and copy the block the, say, 4 to 6 times or whatever.
An alternate method would be to modify the “interval” block such that rather than only the 2 phases, it can be user modified to have 2, 3, 4… etc phases, similar to the way that it comes with a default of 4 cycles of 2 phases, the 4 cycles can be user modified up & down.