Version 6.1.0 has a great new feature: world views are zoomable. Makes a huge difference! Please check it out.
Also, lots of other improvements and bug fixes. See the Change Log at https://physlets.org/tracker/change_log.html for more detail.
To upgrade, click the green "Now available" button on the toolbar and choose Upgrade Now. If you don't see the green button choose Help|Check For Upgrades.
You can also download installers directly from the Tracker home page (http://physlets.org/tracker/) or ComPADRE (http://www.opensourcephysics.org/items/detail.cfm?ID=7365).