Create new document window too large for screen
The window that displays when I'm trying to create a new document is too large for my screen (1280px x 800px).
Even if I hide the dock, the window will not let me make it any shorter (only thinner).
What kind of a Mac are you using? Are you using an external monitor? Can you change your Display Resolution to be larger? You can also change your Dock settings to "Automatically show/hide the dock".
Muthukumar S commented
This seems a window re-size issue.
Can you try re-sizing the XD window (Welcome screen)? Then click on Add-ons tab.