I am rebuilding some old code I made in Zen Cart about 4 years ago.

In that code, I call:
MY_SITE_ROOT/index.php?main_page=doNewThing


on a button, and it appears to call (at least in the old code, it called: )
includes/languages/english/extra_definitions/MYTEMPLATENAME/doNewThing.php

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HAS THIS METHOD BEEN DISCONTINUED .... I mean this way of doing things? It's not working in the current version of Zen Cart.
Basically I had a bunch of custom pages and I'm seeing all of them in
includes/languages/english/extra_definitions/

these pages had custom code in them that I had written, like adding items to wish lists, viewing wish lists, etc.

any help would be appreciated, thanks.