Field help (PLISEA) 

The search groups allow the association of logical price list sets, which are evaluated by priority order within the same group.
Coming from the search group evaluation, the most favorable price list is taken into account for the document and applied to the calculated net price.
It is possible to define up to 10 search groups (0.9). if no group is determined (all the price lists have a zero value), it is the priority rule that will be applied to all the price lists.
SEEINFO The search groups do not apply to the grouped price lists.