Let Finder display files with a user-defined extension I have defined myself a file extension .ev, they are actually text files, which can be opened by TextEdit.

In Finder, by Column view, a .txt document can be displayed directly on the right hand side. Does anyone know if it is possible to let Finder show .ev as well, it will be more handy:
Download the latest QLStephen.qlgenerator (direct download!) from the QuicklookStephen GitHub project. Unzip the file and move it either to /Library/Quicklook or ~/Library/Quicklook.

Now you should get a file preview either in Finder column view or by choosing the file and hitting the space bar.