Board Thread:Support Requests - Getting Technical/@comment-36237969-20200601215121/@comment-168424-20200601222807

Go to a page, at the end of the URL type "/name_of_subpage" (replace "name_of_subpage" with the name of the subpage you want), press enter, click the link after "Create article".

Or...

Go to Special:CreatePage and type the name of the page followed by a slash (/) and name of the subpage, i.e. "PAGENAME/SUBPAGNAME".