Option to play sound instead of displaying balloon on clipping

Option to compact database size on command (or automatically on exit)

Tag picker control

Warn about adding duplicate / similar notes

Color scheme customization

Recognize tags in note's text and make clickable

Add simple status flag icon

"Copy to CN" and "Paste from CN" buttons in window titlebars

Auto-hide and show when docked to screen edges

Option to set tag sidebar visibility on per-notebook basis