In version 9 we were able to modify the settings in the tools palette to set the default settings for line width or text box while no project was open.
However in QuarkXPress version 10 this can be achieved by the following steps:
1. Create a new layout.
2. Create a text or an image box
3. Modify the settings in the measurement palette
4. Go to Edit > Set Tool Preferences from Selected
a. For Current Layout; It would repeat same settings for the tool
b. For New Print Layouts; this would set it as default for all the new layouts as well as the current layout.