I've had the same issue, to fix it: On a MAC OSX go to user or "USERS" ( if many users ) > if the folder didn't show up it means hidden, so press " Command + Shift + Period " on the keyboard to unhide files and folders than the library folder shows up then go to /Library/Application Support/Adobe/Common/Motion Graphics Templates/ aaaaand voila.


Steps for Adding MOGRT folders in Premiere Pro
Motion Graphics Templates files also known as MOGRT files do not need to be installed individually, it's highly recommended that you don't if you have multiple files. This method will allow you full access and control of your MOGRT file/folders within PR's platform and provide you with additional tools to increase your organization, productivity, and workflow.
Please follow these steps below:
1. Create a folder anywhere on any storage location. (e.g I used my "C: Adobe\Documents\Adobe\Premiere Pro" and named it 'Motion Graphics Templates,')

2. Move or Copy your Folder(s)/Files(s) to your newly created folder.
3. Expand the "Essential Graphics" panel.

4. Click "Manage Additional Folders ..."

5. Click "Add"

Click each folder you would like to add. (Keep in mind this will add one folder at a time, this process does NOT support subfolders or nested folders, so add each folder individually).
6. Once you have added each of your folders containing your MOGRT files click "OK"
7. Uncheck "Libraries" and check the "Local" checkbox. (Typically people don't use the preloaded templates if they have downloaded their own, so clicking "Local" will provide you with full access & control of your folders/files which is typically most designers ' preferred' option, in Premiere Pro 2020 you have the option of selecting "All" in the dropdown menu if you would like to display the preloaded templates as well.
This option provides you with a lot of flexibility such as linking either locally to your desired location on your PC, or you can link a cloud storage device also, such as "Dropbox, OneDrive, Google Drive etc." additionally, any files that you add to your linked folder is automatically updated in real-time, in Premiere Pro
Once your folder is linked and loaded inside Premiere Pro's interface you'll have much more flexibility and organizational controls such as; sorting options, setting your favourites, and adding new files +

Good luck with your designs, I hope this helps!