If you see in the Office Add-Ins under the “Managed by your administrator” tab that there is no connection to the catalog, a quick workaround is to use so called “sideloading”.
Before you start, please download this file first:
SlideLizard CreatorAfter downloading, follow the steps of the tutorial below for your operating system.
Windows
Start by creating a folder and naming it “Shared Folder”. Now insert the previously downloaded file (SlideLizardCreator.xml). Then open the folder properties, select “Sharing”, and click the “Share” button.

To access the folder, you need to add yourself and any other users you want to share the add-in with in the “Network Access” dialog box. It is important that you have read and write access to the folder. Once you have selected the desired people, click the “Share” button.

Once you have received confirmation that the folder has been shared, save the full network path that appears directly after the folder name.

Then open PowerPoint, click on the “File” tab, then on “Options” and select “Trust Center”.

Afterwards select “Trust Center Settings”. Now you can insert the previously saved link. You may need to edit the link, make sure to check if there are two “\” characters before the link, if not, add them manually. Before closing the window, select “Show in Menu” and then click “OK”.

Once these steps are completed, you can go to “Insert” and open your add-ins. Now a new tab “Shared Folder” should appear. Your add-in should now be in this tab!
Quelle:
Mac OSX
/Users/<username>/Library/Containers/com.microsoft.Powerpoint/Data/Documents/wef
Copy the above link and paste it into Explorer to find the “wef” folder. If this folder does not exist, create it manually. Then you can insert the previously downloaded file (SlideLizardCreator.xml). Now open a PowerPoint file and select “My Add-ins” through “Insert”! Your add-in should now be displayed!

Quelle:
https://learn.microsoft.com/en-us/office/dev/add-ins/testing/sideload-an-office-add-in-on-mac