So I have some different opinions from NL and Der on learning TT. *NOT* saying they are wrong and I am right. Only that everyone is different. In general it is smart to listen to your coach and trust them to guide you. But I'll put this out in case anyone finds it interesting or maybe we can have a fun debate.
I would not want to put any time into BH flick if I were you. Imo training things that won't often arise in matches at your current level is undesirable. This assumes training time is very limited. But that's true for 99% of adults. This preference is based more on psychology than logic. NL supports learning advanced skills as early as possible. I personally had this conversation with him about my own counterlooping. But NL also doesn't get upset about missing the table. So he could use the advanced skills in match play even if his success rate was low. I put too much emphasis on winning practice matches and would shy away from a counterloop or a bh flick if at first I only made 30% of them say. And if you won't use it under pressure then it will never get any better in matches. So it's useless to train things you don't yet have the courage to use for reals.
This is not right or wrong. You just need to know what kind of player/person you really are when it comes to tolerating mistakes/failure/losing meaningless training matches.
About there being many different strokes each for backhand/fh/flicks/ etc. This is true in a very real way. But I don't find it to be a helpful mental construct for most people. It implies you have to choose between a few options under super tight time pressure for every ball. This stresses people out, we tighten up our muscles, play all stiff like shit, step back for more time we don't really need and take balls too low, and lots of unwanted and unnecessary things happen in reality all because of this false construct in our minds.
I prefer to think about it like this. Every player has only one backhand stroke. One fh. One bh flick. One of each major thing. But every ball comes with a different location relative to your body, speed, spin, trajectory, and so on. We adjust our one stroke to fit the ball. The purpose of anticipation, footwork and timing is to make the required adjustment as small as humanly possible. But there will always be a range of adjustments from tiny like opening the bat 1 degree more, to massive like moving your elbow 18 inches diagonally up and to the right to play a full-chicken-wing backhand. It doesn't look like the same stroke. There is massive logic to thinking of it as a totally different stroke. But imo it is very much not helpful to think that way. It's the same stroke, your one and only backhand stroke. You just did a poor job of movement on that ball, meaning your opponent did well. Life goes on, play the next ball.