add the possibility to add own file extensions for 'Display' like .MTS or .MKV ,show all files are not the best way

All file types supported by Zoner Photo Studio can be turned on/off under display. MTS and MKV are not supported by the program. The need to set the display to an unsupported file type, in a situation where it still makes sense to work with Zoner Photo Studio, is rare. Thus it probably doesn't make sense to add this to the Display preferences.

You can still filter the listing by your own file type using the Filter button on the Manager's toolbar, or the Filter item in the Manager's Organize menu.