I know ya have to root it first, but how do you actually get new tips?

Mine have always done it naturally. I didn't do a thing except keep it watered and give lots of sun.

Kajundude. Plumeria bloom on the tips of the branches, and then they - usually - branch after they bloom.
You can force branching by cutting off the tip, but you are then also removing the chance of flowers for that season.
Here is a picture of an inflorescence (aka inflo, or flower stalk) and you can see how it is making two new branches at the base.

Dutchlady1 said: Kajundude. Plumeria bloom on the tips of the branches, and then they - usually - branch after they bloom.
You can force branching by cutting off the tip, but you are then also removing the chance of flowers for that season.
Here is a picture of an inflorescence (aka inflo, or flower stalk) and you can see how it is making two new branches at the base.

Recently acquired a Grafted Pink Maya (variegated) from TwistedTropicals has a 36" single stem... It's developed 4 leaves with _no side branches YET but, debating cutting it down to 15" & rooting the top... Scared that the lower half might not survive/branch... Opinions ?

If the plant is healthy the lower portion will branch out.
36" single stem is very tall.