How to customize your palette view is very detailed in the help. Did you look at the subject. When you customize a palette, you are creating a .mnu file. It is the .mnu file that modifies the palette. So, just place the VIs you want in the appropriate location and edit the palette to show them. You have then created the .mnu file you want to distribute.
You are not forced to use the User.lib but for custom toolkits, I would recomend it. For instrument drivers, you should place the files in instr.lib. NI places their toolkits in vi.lib\addons.
