@Brecht Van Lommel (brecht) , ok thats a pitty, but I if its a technical limitation I understand at least Blender have the option to choose left/right moste software do not have this choose anyway. Does this also apply to the Spacebar Action? I have found mysealf changing the keybinding and then later on forgot to change the spacebar action from "Play" to "search". Is their any way I can go back and change the spacebar Action after I have saved the new keybinding preset?

In Blender 2.8 Beta: When saving a customized keybinding (adding a preset) the "Preferences" box where you can choose left/right click and spacebar Action disappears, I believe this is a bug?

I think it's in the biggest innterst for both Blender aswell as the users to have a LMB,