If you want to see what the default shortcuts are for using the Merch Wizard shortcuts in Chrome, just copy/paste this into your Chrome browser, you can quickly select it by triple clicking anywhere on the green text:


chrome://extensions/shortcuts


Scroll down the page until you find Merch Wizard and you will see the four assignable extension shortcuts and their default values, they are:


Activate the Extension
Alt + W
Opens & Closes the Extension window. This shortcut replicates clicking the icon to open it and clicking away from the window to close it
Relister - Populate Controls
Alt + R
This shortcut emulates clicking the 'Populate' buttons on the Relister pages
Submit Product Confirmation
Alt + C
This is the final popup window that opens on the final Merch by Amazon submission page to confirm the submission of your product listing for approval
Submit Page
Alt + S
This is the 'Save' button on each Merch create page


If you prefer to set your own shortcuts, just click in the field for the one you wish to change and key in the new shortcut. Click away from that field and it's saved automatically. 


This animation shows the process on an Apple Mac, so the Alt symbol is shown. This is what Alt D looks like: 



Here you can see how to change two of the shortcuts, just click the black X circle to clear the current value, click in the field and then whatever keystroke you enter next will be saved. Please bear in mind, that Chrome has many shortcuts reserved for it's own use, so be careful not to assign a shortcut here that will conflict or you will have problems. For example, (on mac) if you assign Command Q, it may open the Wizard, but after that, it may Quit your Chrome browser and that would be very frustrating :)