There are a few utility classes in Freeplane that are of special use for scripting. Look up their API in the Freeplane scripting API docs, for example coming from the menu - Help -> Scripting API. Here are the direct links:
UITools
Available via the shortcut ui, e.h. ui.frame instead of UITools.getFrame(). See it's API.
TextUtils
Mainly gives acces to available translations. Use the shortcut textUtils, e.h. textUtils.getText('invalid_url', 'The URL is invalid'). See it's API.
HtmlTools
Available via the shortcut htmlUtils, e.h. htmlUtils.toHtml("bla\nbla"). See it's API.
LogUtils
Gives access to Freeplane's standard logging facility, see it's API.
FreeplaneVersion
FreeplaneVersion.version is the full current version (like "1.2.20") but FreeplaneVersion has also accessors for major, minor versions etc. See it's API.