I'm not sure this is what you are asking... but...
In the Grails plugin manager in STS there is a way to 'upgrade' a plugin. I.e. you have some plugin 'foo' verion '1.2.3'
you can upgrade it to verion '1.2.4' using the UI. When you do that an upgrade is essentially executed in two steps:
a) grails uninstall-plugin foo
b) grails install-plugin foo 1.2.4
There may be faster ways to get this done as well (e.g. edit your application.properties file and replace the version numbers in there with what you want... then after that run "grails compile".
Doing "grails compile" should uninstall and install things as needed so that the plugin versions will match what is in application.properties.
The second method is faster but can break when installing some new version of the plugin also implies some changes in plugin dependencies.
I hope that answered your question.
Kris De Volder -- SpringSource