Is there a better way to do trans fluid line

??? There are all kinds of fittings "in the world" but if you are using steel/ metal/ aluminum/ etc tube, flare is the "weapon of choice." So you have inverted flare, SAE/ brass type 45 degree flare, and JIC/ AN which is 37 degree flare. And you could use a made up braided flex line of some sort

The newer stuff for magnums I'm not sure. It seems to be ?? metric?? flare or similar