Complex question about dynamic UMG HUD for Spells

Hey! Thanks for reading and possibly helping ;D
I’ve got quite the situation to handle here!
I created a few spells, a “grenade”, a teleportation etc… in my game, and a skill tree to unlock them by spending points you get by killing ennemies. Simple as day. The less simple part is about getting that result:

192361-skills+in+game.png

Or with the skills exchanging places, depending on which skill you bought first. I want the player to be able to choose up to two skills in a list of between 5 and 10 that appear in my spell tree (so far i’ve not put them in so it looks like that:

)

and i want the first skill they buy to appear in the right image (these are actually buttons).

Here is the BP for the Grenade button on my HUD (it’s the only one i’ve added so far, the second skill you see in the first screenshot was actually photoshopped in.)

And here is my Spell Tree’s BP:

With all the info i gave, could anyone skilled enough in UE4 actually give me clues on how i should proceed? I’m super lost! I’ll answer any question for precisions.
Thanks a lot, people. I swear it’s the last time of the month i ask for help here xD