A Borderlands 3 skill tree appeared on the internet recently, made from Seigler. That skill calculator, which is available here is not complete yet but gives some good information about 2 of the main characters.
Indeed the tree for Fl4ke and Moze are missing but the one for Zane and Amara seems complete. If you are willing to play one of those characters, this tree can help you to plan in advance which skills you would like to unlock first. Mostly considering that there is now 3 different tree for each character.
We have discussed Borderlands 3 recently here and more information seems to appear day after day.