Currently you can right click the insertion palette and change the position / menu items that are shown / hidden in the insertion palette from a context based dialog box. (can also be done from the same box in the type palettes view).
It would be useful to be able to modify this programatically.
Currently you can only programatically play with the typepalettefilelist from the engine property object and insert new ones or remove old ones.
If a sequence file is loaded that has a step type in it that is not currently loaded by a type palette file, then it shows up in the insertion palette (as it should do), but if the testexec.ini file says this should be set to "hide" then it is hidden.