Thanks for your help. I'm gonna try to dive in, following your explanations. I've got to get used to the objects and really understand their functions. What I could do already - as you advice in your comments - is to duplicate the whole thing and thus use one instance of the patcher for 2 different loopers. That makes sense as I found awkward to have to use 2 midi tracks for that purpose. Well, that's already something I was proud of
Actually, for that particular task - telling the SS leds and dispaly (I hope) to follow the Looper state - it is much more elegant and logical to use your solution. Meanwhile, unless I become a M4L specialist, I think I'll still use BMT for some stuff like turning absolute controllers to relative, some double triggers, timers etc.
Don't be surprised if I ask for more help from time to time.