Hi Martin,
combination creation is called in many places, e.g. in F4 help, to calculate the result set in queries (based on the 'access mode for result values setting'), in disaggregation in the query, in some planning function types. The CREATE method of your exist is just one end-point; many other things may happen 'above' your exit implementation.
You may set a break-point in
CL_RSPLS_CR_CONTROLLER, IF_RSPLS_CR_CONTROLLER~CREATE
this is the central entry point of combination creation.
Point 1 in my previous memo is no 'setting' but an explanation how AO calls the F4 help, cf.
CL_RSR_OLAP_PLAN, IF_RSR_OLAP_PLAN~CREATE_PLAN_PROPOSAL
if you are interested in details.
Regards,
Gregor