It would be great to have a Close button on the command bar for all entities in Model-driven apps when Auto-save is enabled. There is currently no way to "navigate away" from a form without using the browser's Back button, or returning to a default view to a sub-area in the SiteMap. The current workaround is to remove the enable/display rules on all Save and Close buttons, which is both time consuming and produces inconsistent results due to the potential for multiple form pages cached within the browser window.
the desired behavior for a Close button would be to return to the last View and/or SiteMap area where the current entity record instance was launched. for eg, if opening a record from a system view, closing that record would return the user to that view. If launching the record from the Relevance Search UI, the user would return to the Relevance Search, etc.