Guys this is NOT complicated. The answer to ANY high-frequency program that has to be condensed into less days is always the same: STOP SEEING A TRAINING PERIOD AS A CALENDAR WEEK. If you can only train 3x per calendar week but a training plan has 5 or 6 sessions in a TRAINING WEEK then simply rotate through the days when you can train.
For example if a plan calls for the following schedule:
MONDAY: day 1
TUESDAY: day 2
WEDNESDAY: day 3
THURSDAY: OFF
FRIDAY: day 4
SATURDAY: day 5
SUNDAY: OFF
But you can only train M/W/F simply do this
MONDAY: day 1
TUESDAY: OFF
WEDNESDAY: day 2
THURSDAY: OFF
FRIDAY: day 3
SATURDAY: OFF
SUNDAY: OFF
MONDAY: day 4
TUESDAY: OFF
WEDNESDAY: day 5
THURSDAY: OFF
FRIDAY: day 1
SATURDAY: OFF
SUNDAY: OFF
Etc. Just roll through the planned days.
I think a mistake people make when they have to scale down the number of days they are training is to try to compensate the lack of frequency by upping the volume at each session IMHO this is a mistake. YES you might be able to do a little bit more work but not that much. It is much smarter to simply do the same workouts spread over more days.
Anyway, and I’m sad to say this, you cannot get the same results from 3 days a week as you can from 5 or 6. So might as well favor performance at each workout (which will decrease if you do too much volume per session) and recovery.