Hi Pilou - it should be possible to do that by a script. Try the attached custom command.

To install it, copy the RotateObjects.js file into the \commands sub-folder underneath MoI's main installation folder. That will make a new command named RotateObjects available to run either by setting up a shortcut key or by pushing Tab and typing in the command name.

Select the objects you want to rotate before running the command, then when you run the command each object will rotate by 90 degrees around its own centroid point.

Hope that does what you needed!

- Michael