how do i make my own nannies

Easiest way is to simply install the UI cheats mod. It doesn't actually change the game in any way. It just makes the options available by shift-clicking on sims. Much less hassle than typing commands.

I use it all the time. I have edited nannies, maids, bar people, repair people, pizza delivery people, the living statue, DJs and more. Pause game, shift-click, edit, back in game.