How can I make this less expensive?

when I use a material function to make glass materials invisible, they still seem to appear in the reflection of mesh objects with the glass that are not invisible. (might be a bug?) So..

I’ve made a function to fire off and hide these windows when I’m just isolating the plot I want in view -

however it’s expensive, i noticed a short but noticeable dip in FPS, So.. what would the most effcient way be? I didn’t set up the tools I am using, however I know enough to work my way around the system.

Could I save all the windows in a variable per plot (each plot is a BP with children static meshes), could this be done before game start? that way I’m not constantly getting items that will always be in the scene.