How are Sanctum rooms banked?

This mechanic is pretty confusing for me. How do you actually bank rooms for later? Do you just enter the void thing and leave? Do you select from the book then leave? Would love some explanation on how the whole thing works.

While in the Sanctum subarea (the antechamber), open the Sanctum Map, click the “store room” in the lower left corner:



This will teleport you back to the outer area, sanctum entrance has gone. I had to reload my char to get the effect displayed:

Cool thanks.

I entered the sanctum and clicked on "Store Sanctum Room for later". Exited then reloaded character. Nothing seemed to happen other than I now have "(Stored:1/8)". Both the room I just completed and the next 2 rooms are still there. What room was saved and is there any way to view it?

(Edit)
I think this is how it works: You store not the room itself but the option to pick a room. You then get a staircase that goes to "Templar archives" that you can run the floor like normal at any time. So basically if you get a warp to the sanctum and don't want to run it right away you can save up the option to run a room and get out and just keep running your Map/Area with out interruption.

Yep tried it and that is indeed it. Thanks!