the copy/paste implementation by Stefan K. opened an easy way for adding a
flexible template architecture to JChemPaint.
Please find attached a plugin jar (copy to $HOME/.jchempaint/plugins). Opening
it (compile JCP from an updated CVS) will show you the 20 common amino acids,
which were originally drawn with JChemPaint and put into a CML file :)
Anyway... clicking one of the structures puts it on the clipboard (you should
be able to paste it to other MDL molfile aware programs too :)... so that you
can then paste it into JChemPaint.
Note that pasting in JCP was not working properly for me... i.e. it pasted the
structure properly, but there goes something wrong with getting the 2D
coordinate translation right...
Obviously, this setup allows *easy* creation of other template plugins for
other structures, like complex ring systems etc...