How do I modify the Project (in GTD.urd)?
 

I'm trying to modify the Project item in a copy of the GTD.URD file.

Oh, an specifically: I want to change the Default Child to ITEM (instead of project)

http://www.kinook.com/UR/Manual/index.htm?template.htm

The defaults are set in Attribute pane (Ctl+4) of the Template for a project. I am guessing you want the default child item to be a Task?

In the Data Explorer window (Ctl+1)- select the Project Item in the Template folder. In the Attributes pane (Ctl+4), change the Attribute " Default Child Template" to Task.

Change default for ALL project
 

Can I change the default behavior of the underlying template (so that ALL projects have that setting (Default Child ...=Task) ?

Re: Change default for ALL project
 

Yes..if you changed the "default child template" attribute of the "Project" item in the "Templates" folder (as above) that should have been the result.

Edit>>Not completely true...if you already edited the item's "default child template" attribute (not the template's attributes) to say Folder then changing the Project template will not change that edited project.