Custom style with my preferred font, does not persist when I open a different document?

This is basically a follow up question to
https://superuser.com/questions/764828/how-can-i-set-up-a-shortcut-key-for-changing-selected-text-to-a-preferred-font-i/

I created a custom style with Segio Print as the font, but it does not
persist when I open a different document?

I created a blank document and made the custom syle again and saved it as a
template.

Then I set the template as default.

When I open up a blank document I can see my style.

But when I open up an already created document I am not able to see the
custom style which I made.

As you have discovered, custom styles are stored per document, and the closest you can get to generality is to save them in templates - even a default template, as you have done. But once you have created custom styles, you can load them into other documents. Open the Styles and Formatting window, click the "New Style from Selection" button, and select Load Styles... . You can load specific styles from other documents or indeed from templates.

I trust this helps.

Brian Barker