You can start the Procedure Editor from Developer Studio by clicking the highlighted button.
The Procedure Editor will contain the currently active file from Eclipse. It is running in the progress process from Developer Studio that is used for compilation of the current project. So all files you start this way will be executed using the same process (as long as you do not restart the OpenEdge AVM).
In the Procedure Editor just hit F2 to execute the file. Note that this will only work for procedure files, not for classes.