Short Answer: No.
Long Answer: Sorry, No.
First off I know nothing of how the palette works, neither do I want to.
Second I have my own projects to get on with (else no deep knowledge) .
Third I suggest that you take the perspective of @kevin192291 and offer to pay someone to help you.
Fourth what benefit would I have in a "step by step guide" of how customise the palette? I've done much writing on NodeRED and created several node packages yet no one knows how to use the sponsor button at github.
Fifth I don't do unpaid consultancy work - any longer, I'd rather do stuff that interests me. If there is an overlap to what others are interested in, then so be it.
I don't mean this answer to be disrespectful, I'm just being blatantly honest. Folks seem to think that because its "open source" everything is "free" as in financially free. That is not the case. Even open source developers have to pay rent and food and insurance and taxes and water rates and drugs - my landlord doesn't tell me that his apartment is "open source" and I don't have pay because its "free", no no no, he comes every month (as sure as death and taxes) and wants money from me. He's not interested in how many folks I helped in my open source activities, nor how many lines of code I created and that were then open sourced for the betterment of society. Nope. All of it does not interest him. The only "interest" he knows is the interest on the money he's making on the rent I'm paying.
EDIT: P.S. This view is totally and absolutely my own and does not in any way represent anyone else here in the forum, the Node-RED community or in fact, the universe. So please don't think I'm speaking for anyone else other than for myself.
