How to place an Associative Pattern and turn off the display of the bounding element?
Place the Pattern with the "Associative Region Boundary" setting toggled on - When on, patterning can be placed on a level other than the level of the patterned element. The Level of the bounding element(s) can then be turned off via Level Display/Manager.
https://communities.bentley.com/products/microstation/w/microstation__wiki/25538/how-do-i-attach-a-cell-as-a-pattern-within-an-element