The Elements Auto-Joiner tool within the Adjusters group from the Project Process tool-set can help join geometries of element kinds of concern automatically in the scope of the current model.
After the ribbon button is clicked, the tool asks for what categories to concern. All of these categories can be checked on or off. Users can also drag & drop each to a different place so as to get them sorted.
In general, the tool follows the order from top to bottom to join those kinds of elements. For example, in the above case, Floors will always be the first joiner.
A progress bar will appear to report what is going on.