Forgive me if I posted something similar before ( can’t remember). I’d like to see a full instructional dvd devoted to what is “ impossible “ to do or at least not wise. The little things like trying to hold the cb when near impossible or trying to use English to straighten out off rail when angle is too extreme to do it etc etc. So many times have I and others fallen into the mistake of doing something we “thought we could do” only to lose because of it. Yes, at the table I suppose I could figure it out but I like to see others opinions and thoughts. Maybe title it “ what you can’t/shouldn’t do on the pool table “
For each player there will always be shots at the edge of their competence, such as, Is your soft draw at an angle good enough to come back without bumping into that close-by ball?, and your examples above. The problem is that as your skill improves the frontiers of your area of competence move back and sketchy shots become routine or at least available. I think the best approach to such shots is to spend some time practicing them, and especially the ones you have trouble with in games, to push back that part of the frontier.
As for a list of them, many progressive practice drills that are already out there will get you to your frontiers. An example using the "forbidden triangle for the side pocket" idea above would be to place the object ball a diamond from the long rail, shoot it in the side, and adjust the difficulty by moving the object ball towards the end rail (but always a diamond from the side rail). That would let you both find your personal triangle and also help to reduce its size.
For those not familiar with "progressive practice" sorts of drills, here is an intro:
http://www.sfbilliards.com/Misc/progpract.pdf There are also several in the Billiard University exams.