The answer was very helpful.
A:=s->plot([L1(s),L2(s),L3(s)], color=red, scaling=constrained, axes=none):
for n from 0 to N do
plots:-display(seq(S[n]$5, n=0..N), insequence=true);
Now imagine again that the lists L1, L2, and L3 contain hundreds or thousands of coordinates such that saving the new sequence of plots (S[n]:=plots:-display([A(4), A(4-n)]):) is cumbersome and undesirable. Is it possible to plot the new isoceles triangles without saving their sequences in the background (Maple's memory)?
Can the whole procedure be done using the "animate" command instead of plot+insequence (to be able to show traces)?
Thanks again for your much appreciated help