Lümmel, to take care of this problem of yours I feel like you have to use a script-program, since the way Relic does things - simply sucks :/ I have only heard of Luvnest who actually use the Num0 key
This was also a problem of mine, I have it binded for my mouse - yet in the very beginning I rarely used it anyway. I think you just have to force yourself to use it untill you simply don't have to think about it anymore and it becomes a natural thing for you to do. Cause it will help a lot in some battles!
ps. please keep in mind that the tacmap isn't nessessary to get amazing at this game. But for some, it really helps a lot! It sorta depends on your playstyle!