Storing Items + Text in a GUI (Procedures)

So i want to create a painting wand that when shift right clicked on ground, it opens a GUI (Pictured). This works great however when i leave the gui screen, the text is not saved and the item returns to the inventory. Is there a way to change this? (Perhaps with NBT tags?)

I cannot use the inventory in advanced properties, as there is no way to change how its opened.