This holder is designed for indicating silica packets. They usually contains color-changing “indicator” silica beads that will change color when it's saturated. This container lets you easily see the indicator beads color from outside of the AMS without taking it out, so that you can easily tell if you need to recharge the silica packets or not.
I have not tested with the original Bambulab AMS - please leave in the comments section if it works/doesn't work!
Silica packets from the pictures are from: https://www.amazon.com/gp/product/B09NVN5C5Y
Dimensions taken from the original model, which works mostly except that its frontal “slots” are too thin to see the indicator beads (which is understandable since it was designed for containing loose silica beads, so it must not have big openings).
The author remixed this model.