A number of mode files for the jedit editor are distributed as part of the jstools package. The mode files allow jedit to support different editing modes, depending (typically) on what kind of file you're editing.
The mods currently distributed with jedit are:
code - generic mode for editing source code
exmh - mode for composing mail from within exmh(l)
hook - test mode
jdoc - mode for composing hypertext documentation
mail - generic mode for composing mail messages
mh - mode for composing mail messages using MH
note - obsolete; use richtext mode instead.
richtext - generic mode for editing multi”font text
tcl - mode for editing Tcl code
The files that define jedit modes are named mode-mode.tcl, and they're normally located in the jeditmodes subdirectory of the jstools library directory (typically /usr/local/lib/jstools). If you want to change or enhance the behaviour of any of these modes, you can make a directory called ~/.tk/jeditmodes (i.e., jeditmodes in the subdirectory .tk of your home directory), copy the mode file for the mode you want to change to that directory, and edit it to your liking. You can also create completely new modes for yourself by creating new files in ~/.tk/jeditmodes. Information about writing and modifying editing modes is available in Programming with jedit under Writing Editing Modes.