Board Thread:Support Requests - Getting Technical/@comment-30398052-20170328172850/@comment-168424-20170329003633

If you make a page into a redirect to another page, it's history is preserved if you do it manually. Using rename too many times can sometimes lose history, especially if you delete something on rename.

Just add stuff from the obsolete page and add it to the new page. After that, replace the contents (in source edit mode of the obsolete page with:
 * 1) REDIRECT New page name

The obsolete page will still have all it's history, if you need to refer back to it.