Setting partitions is not available. If you use partitions, the default partition that is defined under Account Settings is used when creating project and tasks.
The following lookup values that are defined in Classic CA PPM SaaS are visible in the New User Experience:
Lookup values that are directly associated with the System partition Lookup values that are associated with a different partition with the partition association mode set to include ancestors. The include ancestors mode exposes the values to the System partition.
If you created string/number type of attribute in non system partition you should see those attribute in the New User Experiencing via Blueprints. Also please remember only attributes available on Project and Investment objects could be selected to be included via Blueprints.