This feature is an extension included in Ext.NET 5 and previous versions, and currently Ext.NET 7 basically implements what "stock" Ext JS delivers. We are gradually adding support for Ext.NET previous versions specific features, but this extension still couldn't make it into the latest release.
We hope to be able to parse most -- if not all -- Ext.NET 5- extensions, but for now we focused in taking advantage of the most used ones, like direct events and methods, and also include unique fixes to issues of existing Ext JS base that we have applied to Ext.NET over the years.
So for now, I'm afraid this specific feature will not be supported in Ext.NET 7 as the code for it is not present in the base Ext JS nor in UX/extensions code that was ported to the new version.
In general terms, we have issue #1741
logged to track the implementation of initial Ext.NET-specific extensions to Ext.NET 7, so you may want to subscribe to this github issue if you want to be notified when it is implemented.
Hope this helps!