This is a penetrating question.  Of course, the main emphasis is the non-movement, the inertia of inactivity in the plot (emphasized by the important last line: “They do not move.”)  But there are two other “movements” in any stage performance.  “Blocking” (the changes of position by the actors) and “gesture” (the language of stage gestures, both realistic and artificial, of the actors’ hands, head, posture, etc.)  In blocking, Beckett has prescribed much of it:  Pozzo and Lucky’s entrance, for example. But the director must choose the proxemics (the closeness and distance between characters at any time).  In stage “business,” for example in the burlesque business of changing hats, or the examining of boots, the director must select details of the movements for rhythm and realism.

But what makes your question so intriguing is the overriding thematic idea that movement itself, for Gogo and Didi, is simply a means to “pass the time.”  The meaninglessness of all effort is emphasized by the futility of “action” itself:  “Did they beat you?”  “Of course they beat me.”  This futility is condensed in the scene where the tramps consider hanging themselves on the tree.

Finally, the most condensed movement on the stage is the appearance of a leaf on the tree in Act Two.  Sudden, out of range of the tramps’ control, occurring in the timeless space between acts, it finalizes the purpose of all movement, in the play or in the world: Change is illusionary and meaningless, merely the random fluttering of existence in the winds of nothingness.