“I know I can add my own code to make the default period go to new”
I took this to mean you at least understood the basics of what you’re trying to do. Perhaps we should start at the start: you want links in your posts (at the very least) to open in a new browser window, correct? There are a few reasons why this is not the best of ideas, but if you’re going to do it, you do have several alternatives:
1. Place the following attribute in every <a>
tag you place in a post:
target="_blank"
Issues with this is it’s invalid XHTML, and must be added manually (although one could edit the link Quicktag to insert it automatically).
2. Place the following attribute in every <a>
tag you place in a post:
onclick="window.open(this.href,'_blank');return false;"
There are other javascript-ish methods; this is probably the simplest. Again, it must be added manually (same Quicktag caveat as for 1), but it is at least valid XHTML.
3. Use something like the following javascript in your template(s):
https://www.js-examples.com/javascript/?view=848
This automatically rewrites links on a page, with the side benefit of being able to exclude links within your domain (i.e. “www.337studios.com”), and to offer an option to readers to turn it on and off. It is however another XHTML bad boy, though this can be dealt with in the code.
4. Use something like my Add Link Attribute plugin:
https://guff.szub.net/add-link-attribute/
*Wrapping* a WP template tag in this function allows you to pass one or more attributes, such as ‘target=_blank’, to any links output by that tag. So you could replace this in your templates:
<?php the_content(); ?>
with:
<?php add_link_attr('the_content', '',
'onclick="window.open(this.href,'_blank');return false;"'); ?>
and the plugin slips the onclick attribute into every link. But note this does not offer the ability to filter out those “local” links of yours.
If you decide on the best way for your to go on this but need further help, just ask (just make sure to clarify what that way is going to be).