This is not possible with a plain DokuWiki and i am not aware of any plugin doing that.
But i can imagine it this can be solved in a plugin ;-)
There is a warning note beside this field in the Admin Config that changing it can have "unintended consequences" so I am worried that simply appending ", home" to the existing value is a bad idea.
If you change the startpage option all your links with a colon at the end will point to somewhere else and your startpage of course.