Remove Item from ComboBox Selected
What are you using to populate the ComboBox? Did you hard code it, did you use an expression?
Since your trash can removes it from the Gallery but not the Combobox, my assumption is, you are not populating the combobox the same way you are the gallery itself.
Sure you could update the Trashcan to do this to the combobox options, but need to explain how you are populating the items in the combobox.