TablePress has a large number of WordPress Plugin Hooks (Actions and Filters) in its source code. They provide easy and well established methods to add new features and enhancements to the plugin, or to alter plugin behavior. A more detailed explanation can be found in the WordPress Codex.
There are some examples on how to use these hooks on the Extensions page.
The advantage of using these hooks in contrast to modifying the plugin’s source files is that the changes will still work after upgrading the plugin, and that they can be maintained separately.