This Contao extension backports the support for automatic dynamic parent tables to Contao 4.9. This is a feature that was added to Contao in Contao 4.10 (see this PR). This enables you to utilise tl_content as the child table for your own table for example, without having to manualy set the ptable in the DCA of tl_content dynamically yourself.
Note: this extension won't do anything in Contao 4.10 and higher, but can still be installed in these versions without any issues, so that you can stay compatible with Contao 4.9.