Hello @ahmet_tabak, this (or something very similar) has been proposed and discussed before, about a year ago, here: Onion Skin on/off shorcut for curent active layer (not global)
That didn’t get any votes (I forgot to vote for it but I have now) and the discussion faded out.
I certainly think it’s a good idea as are some other ideas for a quick and easy global disable/enable icon on the Timeline.