Try with 5.2 version of eclipse editor. It can be downloaded from here. I don't experience this issue so I would assume it is already resolved but I could be using latest not yet Final version of the editor. Please post back if 5.2 version solves it or not.
Thanks Maciej, The 5.3.1.Final/org.drools.updatesite-5.3.1.Final-assembly.zip you specified in the link doesn't have the issue. The version which I had issues were below. I am providing the links incase others run into the same issue with these versions.