The settings of the user are stored in folder: /omd/sites/[site]/var/check_mk/web/[user] as what seems to be json files with .mk extension.
I’m assuming when user is deleted their folder is deleted as well with all content they created, whether they shared it public or not.
Perhaps copy needed content as file or parts of file content to another user before actually deleting user.
Alternatively you might be able to get (some) settings retrieved from a back up.