Hello again

It's not a problem to build group menu for first input:

auto whatGroup_PARM = PRM_Template(PRM_STRING, 1, &whatGroupParm_NAME, 0, &SOP_Mantragora::pointGroupMenu);

but how to build it for second input?

There is buildInputGroups() method but I don't know how to use it.

Could we get some example, please?

Thanks!

If you look in SOP_Node.h you'll see there are some PRM_SpareData choices available that are designed specifically to indicate which input the group menus are based on.
PRM_Template(PRM_STRING, 1, &names, &defaults, &SOP_Node::pointGroupMenu, 0, 0, &SOP_Node::theSecondInput)

Cool! Thank you!