However these admin pages only allow me to edit our current theme, not our new theme (still in Draft mode). For instance, if I added a new Page and tried to select the right template, our new dawn templates will not appear in the lists of templates, only our old templates will show up.
So essentially it seems I’m stuck where I can’t edit any menus or pages until our theme goes live. Or am I missing something?
If you want to make changes to navigation/menu’s then it will also affect your live theme.
As there is no option to make changes only for preview theme.
Alternative - Create a new menu and use it in your preview theme. And don’t use the new menu in the live theme.
To assign the new templates which you have created in your preview theme, this templates will not appear unless you have same template in your live theme. So you have to create the template with same in your live theme so it will appear at your admin side.
This worked! I just created a dummy template and page in my old theme with the same name as the new template in the new theme, and then the page would appear in all the dropdowns.