Hello JJ,
Your question is about the variant to be created for IP30 . You need to either put all the maintenance plans (90) into the multiple selection of the Maintenance Planfield of the selection scree OR give a distinct Sort field name for all the 90 plans and the specify this value in the MaintPlan sort field of the selection screen > and then create a variant. Based on this variant you will make the background job.
Also go through this document: Background Job Scheduling for IP30 (RISTRA20)
Regards
KJogeswaraRao