Note Head palette | MuseScore

“In my latest MuseScore version…”
Please always specify which version you are actually using. You can copy this information from your MuseScore Studio menu path Help > About MuseScore Studio… > Revision > (click the paper icon).

… the Note Heads palette has dropped off my list”
When you use the + (plus) sign to add a palette, MuseScore adds the extra palette at the top of your chosen list of palettes. That has caught me out before.

If the palette really is absent (both from your displayed palettes and from the list available in the “Add palettes” list), then you might try the menu path Help > Revert to factory settings