If all you want to do is maintain, you can keep your intensity but drop your volume by 1/2 to 2/3. Either cut frequency or go down to basic compounds or a combination of both, and then make sure to have a dropdown set of higher reps to preserve size.
Example, if program "X" got you big enough and strong enough on 3x/week full-body, then cut down to 3 workouts every TWO weeks and keep the same program. Or if 4x/ U/L split got you there, then cut down to 2x/week workouts.
KYS.
Oh wait, you're a vegan, so you're already doing that, just slowly.
Actually USE your autism to study how people interact, and then fake it 'til you make it.
When you can do 10+ reps fresh, add weight to all sets, and add enough that you can only do 6-9 reps on the first fresh set. When you can do 10+ with that weight, add more weight.
You should be doing SS instead of "legend of he-man named after a castle in a kid's cartoon invented by johnny pain the strength villain who just ripped off SS and who himself started his lifting career using SS."
That said, his bullshit program would have you deload and work up again.
That said, lots of different ways of handling this in your own programming. You could just stay at that weight if you were close to the rep total, you could make up the reps by adding another set, either at that weight or by adding a dropdown set, etc.
Loufa. Salicylic acid astringent. Benzoil Peroxide cream. Getting older.
Warmup like you normally do for your 3x5 working sets and then do a single at that weight, then add 3-6% to it and do another single, then add 3-6% again and another single, with 2-3' rests between singles, the last single you do you can call your 1RM.
Once you have a 1RM and want to break it, warmup as if you were gonna work at 85% of it, then do singles at 85%, 90%, 95%, and 100% either do an AMRAP set or do 100%+ 5-10lbs.