You can edit or delete layout templates within Page Builder while you have any page open for editing.
Tip: The page itself does not have to be using the template to edit or delete the template.
To edit or delete a custom layout from within a Page Builder editing page:
1. Click the Templates button in the upper right corner.
2. You'll see the list of saved layout templates.
3. To delete the item click the X to move the template to the trash. You're done at this point.
4. To edit the item click the Wrench sign. The layout template opens in Page Builder in a new tab. Note the URL changes to mydomain.com/fl-builder-template/.... to show you are editing a template.
5. Make any editing changes, you want, then click Done > Publish. The tab for the layout template closes and you can go back to the page you were editing.
Remember, the edited template does not update any existing templates, so if you want to update the page you're editing, you'll need to follow the normal procedure to use the edited template to append to or replace the existing layout.