In order to get around modern site limitations, a SharePoint framework extension has to be added to provide easy access to site administrative links that have been provided by ExCM Site Actions menu items in previous versions. In SharePoint 2019 Modern Team Sites, the Site Actions menu has been depracated and the new approach to providing custom menu items is to use the SharePoint Framework to add a custom header area to the page with custom links to the ExCM administrative actions positioned in this area.
To add the extension, SharePoint Apps need to be enabled for the farm you plan to work from. You can see how to do that here if the farm does not already have apps enabled.
Once you have a working App environment, you will need an App Catalog to store the ExCMModernLinks.sppkg file. If you do not have an App Catalog for the Web Application your page is on, Microsoft has documentation on setting that up here.
We have found that the Microsoft documentation does not explain an additional step that may be required. If you find that you receive "404 not found" error messages after you follow the steps later in this article, you probably will need to do what a Microsoft representative describes in this blog post.
Navigate to your App Catalog, and go to the Apps for SharePoint section. Once there, drag in the excmmodernlinks.sppkg file that is included in the ExCM installer. This file (excmmodernlinks.sppkg) can be located at "Program Files/PremierPoint Solutions/Extranet Collaboration Manager 2019/Packages" on the server in your farm where you first installed ExCM - which is always the Central Administration server.
The next step is very important to get right. There will be a "Do you trust this solution?" dialog that appears. DO NOT check the "Make this solution available to all sites in the organization" button. Make sure to press Deploy WITHOUT checking this box, or else the extension WILL NOT be visible for users to add to any page.
This text from Microsoft attempts to explain the reasoning behind this:
The ExCM Modern Links extension DOES include a "feature framework definition", so the above explanation makes sense even though the check box on the dialog seems counter-intuitive.
Now you should be able to go to the site and find the app, but before you do that, we recommend adding a site sponsor to the site you are testing with, if it does not already have one. Site Sponsors are the only users that will see these administrative links.
To add a site sponsor to the site, navigate to the Modern sites' Site Settings page, and add a site sponsor.
If ExCM is installed and the site you plan to add the app to has a site sponsor, it is time to add the app (extension). Navigate to the site you wish to add it too, and from the settings dropdown, select Add an App.
The app should be visible under the Apps you can add section, but it might be easier to find it under the From Your Organization section.
Select the modern links app from the page, and it should begin to download it. Once the app has been added, it should be filled in in the site's contents page.
Now if the site sponsor you added logs into the site that has the app (extension) added to it. they will see the newly added modern site admin links:
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