I'm using some special characters like mathematical symbols in different programs like Mail or Adobe Illustrator. Of course I can open the Symbols Table, search for the needed symbol and copy&paste it. Is there a way to define a shortcut to insert a specific special character?
I use TextExpander, myself, so that c== is a shortcut on my system for ⌘, o== for ⌥, and several others, in part because I do not want to lose the symbols already mapped to the option (⌥) key combinations on my keyboard.
On the other hand, remapping the ⌥ keys to symbols different than the ones they are original configured for can be helpful and convenient for some people also, which is where Ukulele shines.
You can use built-in Automator and Services. Look at my answer to the similar question.
You can get very fast access to the symbols via the widget CharacterPal.
Click on the needed icon in order to paste to the clipboard.