This variable determines the character that separates words in a page ID and that replaces characters not valid in a page ID.
_
The page ID is the component of the URL that specifies the page. For example, by default the link doesn't exist goes to the URL dokuwiki.org/doesn_t_exist. wiki:doesn_t_exist is the page ID. The default sepchar is '_', so the apostrophe and the space each appear as an '_' in the link.
By changing sepchar to another character, you can change the '_' to another character. The valid sepchar characters are those that are valid in a page ID: letters, digits, underscore (_), dash (-), and dot (.). The sepchar variable must contain exactly one character.
Be careful with this variable. By changing it you can make pages created under a previous sepchar inaccessible. When you create a new page, the page ID becomes the file name for the page. If you create pages with sepchar '_' and then later use sepchar '-', your links to those previously created pages will break because the links will change but the file names won't.
Warning: Changing this option could cause unintended behaviour.