Inventory management is a pain right now. Not enough space in your chest (just make it huge). The transfer screen is not well designed, you should be able to just transfer from either side without switching sides. Also closing the chest should be the same key as opening it. (windows).
Thanks for the feedback friend! I will rework the inventory system in the future, making the player able to stack up items/divide stacks and make it into a one window, your opinion that it could be much better is absolutely valid and I agree with it. I've made the current design on a basis of an inventory system tutorial about 2 years ago and had not had as much designing and programming knowledge as I do now.