DESIGN > TEMPLATE SETS Admin Tool

Highlights of this feature:

Allows you to have multiple template sets in use at one time
Allows you to manage template sets as a whole without dealing with individual templates.
Allows you to specify which template sets are in use on the client side with a few clicks
Allows you to upload whole Geo template sets at once
Allows you to back up (download) entire template sets at once
Allows you to set a specific template set for use with a specific languages

Where are template sets managed in the software?

As the title of the section says within:

DESIGN > TEMPLATE SETS

DO NOT MAKE CHANGES IN THE DEFAULT TEMPLATE SET!!!!!! It is overwritten with each version update. For more on why see the do no change the default template set page
Each language in your site should have a template set assigned to it.
If all template sets are inactive in the DESIGN > TEMPLATE SETS admin tool the default template set will be used by default
You must have at least one other template set than the default template set in your installation. This "non-default template set" will be where all your design changes will take place.
If there is only 1 active template set besides default one, you cannot change the order, so the column is not displayed
You can only make changes to templates in template sets that are marked as "admin editing" within the DESIGN > TEMPLATE SETS admin tool
If you make changes to templates outside the Geo admin tool make sure to click the "re-scan attachments" button regularly next to template set you uploaded your changes to. Doing this tells the software you made a change in that template set. After each saved change the software needs to run certain behind the scenes routines that update template/module/addon attachments as well as recreate pre-compiled templates in the system.
You must be in advanced mode to be able to customize addon, system and module templates within the admin tool