On Wild SMP we used to be able to put GCs on item frame which was disabled a little before Candy SMP launched. On Candy SMP we still cannot do that.
I personally used to put the GC on the item frame then pull them off from a distance and have a hopper catch them so they would end up in a shulker box which would stack them and it would save me some inventory space and I could store them in my PV safely.
On Candy SMP this is more important now than it was on Wild SMP because we have Keep Inventory off in Candy SMP PVP. So if someone traded GCs with me, I would be stuck with them in my Inventory and would not be able to part-take in envoy events just in case someone killed me and I would end up losing the gems. If anyone knows why GCs cannot be put on item frames or why we can't move them into our PV or EC, please let me know and if staff can help us do something about storing them safely in our PV/EC please assist. Because since the launch of Candy SMP, we are trading quite a bit in GCs and having to consume the GC and then repurchase them back from the server is not very economical.