Hammer-ons and Pull-offs? -- MS4

I understand there is no "H" or "P" available to designate these articulations, that the slur should suffice. However, I am trying to create a custom symbol that incorporates the slur with a centered H or P, to add to my palettes.

Seems I cannot select both the slur + the P and drag the combined symbol to my Guitar palette. So is the only solution to place the slur, then add the P and center it manually?