just ideas:

autocompletion
broken links checking
aspell support for Win32
screenshot function
remember wrap setting //add to the triplex field
comment the selection
Highlight all search results
gradient colorization in palettes
"entity to text" function
fm::detect the charset for the selected file
new image viewer?
autoscroll //useful for musicians. define the speed in bpm?
numbers into words
ctags support
make max recent items user-modified
hl for gas, Lisp
ZIP the directory?
Unzip selected archive
units conversion
PDF text reader
add function to update hls cache manually
unicode table window
split document panel
ANSI art support
play the chords by name, i.e. select AmDm, then use something like "Play melody"
parse the compiler output, goto the error by clicking at logmemo
0-9 markers
QFileSystemWatcher integration
optional charset detection
multiply files charset encoder
goto start/end of the code block
think more about filenames charset in zip-archives //tzipper.c line 75
PalmDOC (pdb) read-only support? http://wiki.mobileread.com/wiki/PalmDOC, http://www.hotpaw.com/rhn/palm/pdb.txt
epub support

