How To Extend A WordPress Plugin Without Losing Your Changes [duplicate]

One way you could try is checking if the plugin provides any actions or filters you can hook into. These allow you to transform data that will be passed around the plugin at various stages of its execution, and also allow you to perform extra actions when something happens. See: https://codex.wordpress.org/Plugin_API

A way to find available hooks would be to search the plugin code for “do_action” and “apply_filters”.