In the Cloud Wiki, it appears as though when you use the include element, the table of contents in the parent page does not show the headers from the included page.
Note in example below, I added a TOC to a Parent Page, Only Displaying Headers from 1 to 2. I added a Header 1 and Header 2 on the Parent page. I then created a child page and added Header 1 and Header 2. I added an Include of the Child Page on the Parent Page under the Header 2 on Parent Page. Note that the TOC only shows the Parent Page Headers.

Old 4.2.6 version of the wiki did not have this issue. See below.

This is a huge step backwards when you have many child pages that you want included on a parent page.
Does anyone know if Atlassian will fix this?