Edit theme for groups still available?

Upgraded sites that made use of these features preserve these features in version 11, however, file inclusion and inheritance options are now a function of Theme Studio.

To still expose these options in new themes/sites, support for including files must be added to the group theme's configuration options (along with the usage of those configuration options).

So I have a theme that used these...how do we expose it?  I don't see any areas where I can add custom styles.  Also how do I include files ONLY for a single group?

Any legacy properties that had values at upgrade time are preserved. If the options are not in theme configuration in the front UI, it's possible that no group had custom stylesheets defined at upgrade time. Alternatively, if the site was upgraded and these options were preserved, reverting the theme implementation can remove these options (since the base implementation no longer has these options by default).

As far as adding these options, it would be a UrlList configuration property (limited to CSS/LESS files) defined in the theme and rendering of those files via $core_v2_widget.GetEmbeddedFiles($propertyName) in the theme's header script and rendering each file into an appropriate <link /> tag using the URL from $core_v2_widget.GetExecutedEmbeddedFileUrl($propertyName, $fileName) (to support processing LESS functions).

Any legacy properties that had values at upgrade time are preserved. If the options are not in theme configuration in the front UI, it's possible that no group had custom stylesheets defined at upgrade time. Alternatively, if the site was upgraded and these options were preserved, reverting the theme implementation can remove these options (since the base implementation no longer has these options by default).

As far as adding these options, it would be a UrlList configuration property (limited to CSS/LESS files) defined in the theme and rendering of those files via $core_v2_widget.GetEmbeddedFiles($propertyName) in the theme's header script and rendering each file into an appropriate <link /> tag using the URL from $core_v2_widget.GetExecutedEmbeddedFileUrl($propertyName, $fileName) (to support processing LESS functions).

What do I pass for "$propertyName" in $core_v2_widget.GetExecutedEmbeddedFileUrl($propertyName, $fileName) 

The ID (internal name) of the property from which the file was retrieved from the theme's configuration. Same as GetEmbeddedFiles(propertyName)