I have run into the problem that I am not able to add other people to trade shop chest unlike normal chests(making them private to me and my friends). I wish you could be able to add players to your trade chest because I store things in the trade chests that I need and my friends need, but they can't get the stuff without me.Yes they can just make a chest storing stuff to and maybe take stuff out and store it but I store most of my things in the trade chests and the only way for my friends to get it is if I'm there but when I'm not and they need the stuff how do they get it??
If it's your stuff you are selling, you shouldn't need to add this. Here is why I don't support: First off, I'm sure there is a reason that this isn't already a thing. It would encourage griefing. Next thing you know, fights could break out. Saying friends took out an unfair amount of money that you deserved and vice versa. This would only complicate things and encourage possible grief. No support.
If you friends were on your island and you have them one the chest why would they steal stuff when they already are on the main chests?? The grieving part doesn't make sense.:eh
Ok yo I got the best plan for you. Make it a double chest but have one trade sign so you can both access the chest and refill etc, I have done this myself with Mrbencraft and it worked out very well for us. So this doesn't really need to be added in, No Support.
There's actually a way around this, but you have to be the person who made the trade chest to do it. Me and Dough do this in CloudMall.