The LiveCode script editor has some basic handler navigation built in. If you right-click on a handler in a script then the contextual menu displays “Go to definition” as an option. This will take you to where the handler is defined. Unfortunately the LiveCode script editor only looks in the same stack for the handler definition. This has limited use.
The included plugin overrides the LiveCode implementation and searches all ‘frontScripts’, ‘libraryStacks’, and ‘backScripts’. You can see an example of how the plugin works in the manual.
If you aren’t familiar with how to install plugins for LiveCode then refer to How to Install Custom User Plugins.