It's easy to convert multiple keywords to person keywords: Select them in the Keyword List panel, right-click, and do Convert Keywords To Person Keywords.
Unfortunately, as you've discovered, to go the other way, from person keywords to other keywords, is difficult -- you have to edit each keyword in turn.
Users would very much like to batch-edit the other keyword attributes as well. But though many have complained over at least the last 5 years, Adobe has not implemented it. It's not even possible to write a plugin that would provide batch-editing, due to trivial oversights in the Plugin SDK. Some adventurous souls have accessed the low-level SQL database in a catalog to make the changes (you can see the forums for possible recipes), but that obviously requires technical skill and is fraught with danger.
Please add your vote and opinion to this topic in the official Adobe feedback forum: Lightroom: Better keyword management
Thanks John, I'll add my vote to the list. I must admit for the amount of keywords I have got I am probably better off ignoring the ability to define them as people or not and just leaving them as they are. Shame really...
Actually, the bizarre thing is that on upgrading to Lightroom CC, it seems all the keywords have been define as both "People" and "Other", appearing on both lists?
On upgrading to Lightroom CC, it seems all the keywords have been define as both "People" and "Other", appearing on both lists?
I just noticed yesterday I had two keywords that behaved the same way. Please add your vote and details to this bug report: Lightroom: Keywords filter as both People and Other
Done, thanks John