Until we get voting reform, the US presidential Election is a binary choice, one or the other. An endorsement is just that: supporting one candidate over the other (and obviously their policies come along with them).

Doing it this way comes across as lukewarm support and isn't as helpful in getting people to vote for that candidate. Kamala Harris is an empathetic, intelligent person capable of introspection. Get her elected, then we can pressure her to reconsider certain policy positions...