Nifty gui Display tap not working

Hey I’m trying to make a main menu for my game with the Nifty gui thing but it’s impossible for me to get the gui right because wen I finish coding the gui and want to know how it looks the display tab doesn’t update and I have to close the tab for my file and reopen it to get the display in the file tab to update. This is vary annoying and would like to fix it, can any one help me?

Thanks in advance!