I see the strings being added to the toolbar with
LPWSTR szBuf = HH_LoadString(buttons[dwIndex].idCommand); ... buttons[dwIndex].iString = (DWORD)SendMessageW(hToolbar, TB_ADDSTRINGW, 0, (LPARAM)szBuf);But from there it's not clear to me they whether they will be used or not. Did you specifically mean that only Jump1/2 would not be used or does that apply to the other IDTB_XXX strings too?
I was referring specifically to Jump1/2 in this case. They do get used, particularly as it looks like we don't currently replace them with the custom text.
However, the "IDTB" strings that we have are all noted as "unimplemented" in Microsoft's htmlhelp.h file, and in theory nobody should be using them. Considering we don't support any of them in TB_AddButtonsFromFlags, I think the resource entries for them can be removed.
James does seem to have added support for creating the toolbar buttons for IDTB_TOC_NEXT/PREV, but I can't find any documentation on what they're meant to do, and he added no actual functionality, so they can probably go too.