Cannot get the thing to work for me in Sam x 3 suites.....I click on the "+" and try to drag the marker to make a 4 bar loop and it isn't happening for me. Instructions flat out not helpful on this topic in the help files.
I'm not sure if you've worked it out yet but to loop an object you need to right click on the object and from the menu choose Object > Build loop object. Or you can use the shortcut Ctrl +L. Once this is enabled you can drag the MIDI object from the bottom right edge to loop. I have a tutorial which shows you how to do it with audio objects but the same applies for MIDI objects: