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I am creating a new footer sublayout in sitecore for use in multiple sites (we run a multi site environment). Currently a sublayout called StandardLayout is used, but I would like to change this across several of our sites to a new layout GlobalFooter.
The problem is that child items of the Home Page have overridden layout components, so what I would like to know is if there is an easy way to change the layout without losing all of the overridden components (as I expect that I may need to reset the layout in order for the flow down to occur)?
I am hoping to be able to just change the top level element (Home) and then have this flow down to the child elements, otherwise this task will become very long and tedious if I need to go through each item and change the presentation to use the new footer.
The icon circled in red in the image above indicates that the presentation has been overridden for that particular sitecore item.
To answer your question, directly, there is no way to apply an update of the presentation details of a template to templates that inherit from it that have had their presentation details changed without losing the changes.
The solution described in the blog post you linked to is the best solution for updating inherited presentation details in this manner. IMHO, I believe that this functionality should have been built into Sitecore long ago as a separate button on the ribbon, and you may choose to add one if you are so inclined. If you do not have the time to do so however, creating an admin page that you later delete from the site after using is a perfectly viable solution as well.
This post appears to detail a way that I can achieve my goal, basically I would create a admin page that does not publish and put the code in the blog into it to update the layout via a button trigger.
https://www.sitecore.net/Learn/Blogs/Technical-Blogs/John-West-Sitecore-Blog/Posts/2011/09/Programmatically-Update-Layout-Details-with-the-Sitecore-ASPNET-CMS.aspx