You can. I believe there is a tutorial on the website somewhere detailing editting the UI, but ultimately the panels on the right are just HTML and CSS like the rest of the UI, so they can be changed around to your whims.
I found this tutorial https://docs.textadventures.co.uk/quest/images.html that goes into better detail on actually adding the image file to your game.
On the web editor, when you run the game you should be able to inspect the element of your browser to look directly at the HTML and css to see what elements you want to edit. If you're using the windows quest editor, there should be a "HTML Tools" or "Developer Tools" button at the top of the in-game UI before you publish which will show the HTML elements.