Since Simplicity Studio is an Eclipse-based development environment, plug-ins can be installed, although not guaranteed. Version control plugins such as git and subversion (SVN) can be used.
As for the setting method, select Add/Remove Packages ⇒ Advanced Install... in that order. From here onwards, repositories can be added using the Add button in the same way as in normal Eclipse. For example, in the case of EGit, add as follows. If you set the necessary parameters, you can use it like normal Eclipse.

Name: any name (e.g. EGit)
Location: http://download.eclipse.org/egit/updates

The setting items of each plug-in can be set from each item added under Simplicity IDE ⇒ Window menu ⇒ Preferences ⇒ Team.
For version-dependent plug-ins, those compatible with Eclipse v3.7 series (Indigo series) can be applied. However, it does not guarantee the operation of all plug-ins.