IJ2 is out
 Sec. 4: Using Keyboard Shortcuts Up Part II: Working with IJ Sec. 6: Undo & Redo 

5 Finding Commands

Navigating through the extensive list of ImageJ commands, macros and plugins may be quite cumbersome. Through its built-in Command Finder / Launcher [48], ImageJ offers an expedite alternative that allows you to retrieve commands extremely fast: PluginsUtilitiesFind Commands… [l]↓.
In addition, ImageJ features a find function that locates macros, scripts and plugins source (.java) files on your computer: the PluginsUtilitiesSearch… command. Because most of IJ source files contain circumstanced comments, you can use this utility to retrieve files related not only to a image processing routine (e.g., background or co-localization) but also to a practical context such as radiogram, cell or histology. Indeed, ImageJ source files contain detailed annotations useful to both developers and regular users that want to know more about ImageJ routines and algorithms.
Search… and Find Commands… [l]↓ are described in detail in PluginsUtilities.
PluginsUtilitiesFind Commands… [l]↓
figure images/CommandFinderAndSearch.png
Control Panel… [U]↓, Keyboard Shortcuts↓ and SourceCodeRetriever, a macro that searches for a menu entry and retrieves the source file of the respective command
 Sec. 4: Using Keyboard Shortcuts Up Part II: Working with IJ Sec. 6: Undo & Redo