An improvement would be to have portion of the screen resizable, especially navigation three panel and the graph one in relationship with the board. Currently you can hide/show each panel but the remaining space is not used by the others.
Very nice the feature that bring to the position just before the move that you double-click on. However a scroll bar in the navigation three would be useful too.
It would be easier reading the graphs if on the intermediate horizontal rules a small number indicate its value (currently only the extreme values are reported and the scale often change in the score and in the rank estimate graphs).
On my Mac, when I save the game and I reopen it, the AI analysis, the variations, and my comments are not restored.
What about adding a weird sound when you play a red/purple move in a teaching game?
Since it seems that KaTrain is oriented to learning (I like it for that), why don’t add a sort of game in the game when you play a wrong move (red or purple) in a teaching game? You would have a second chance for that move selecting only among pre-defined spots (A, B, C … ) each of which are some of the best AI top moves mixed with other few fake (wrong) moves. This to push the learner to think better to that specific move with some suggestions but not to exploit all the options coming from AI (it would be a more proactive approach). Actually you can do something similar turning off the top moves feature and trying yourself w/o suggestions.
Again all my encouragement to improve the product which is very nice.