To change the default leading just make the change with no documents open.
You should get this reply automatically by email from the forum, there is a button to not get it.
The leading-as-percentage-of-font-size-control is in the Justification window. It's a paragraph-level attribute, not document-level or application-level. So, you could set it with no documents open and no paragraph style selected, and then it would be the new default for all new text with No Style. You may want to edit the widely & justly hated Basic Paragraph Style's Justification settings as well, while you're at it.
Did as you said and also did indeed get it in email. I thank you. Project
closed. Do I need to do something to properly close this thread?
A step at a time. Project One annihilated. Thanks.