Eclipse allows to trace a running Eclipse and to write information to the console. This can be used to identify which command is associated with a certain keybinding. To use tracing modify your runtime configuration on the "Tracing" tab and set "Enable Tracing". For trace for example the keybindings of "org.eclipse.ui" plugin select it and flag "debug".

Scroll down and select "trace/keybindings" and "trace/keybindings.verbose".

Make sure you have the -consoleLog flag maintained as an argument.

If you start now the Eclipse IDE and you use a shortcut the calling Eclipse will display a trace which contains the commandId.

In your calling Eclipse you can now use Search (text) to find the handler / action which implements this command.