Try these:
  [apply] [grind
    .] for pattern: [@Membership.mem #4 (List _) _ #1 #3, @Membership.mem _ (List _) _ (@List.cons _ #2 #1) #3]
  [apply] [grind →] for pattern: [@Membership.mem #4 (List _) _ (@List.cons _ #2 #1) #3]
  [apply] [grind! .] for pattern: [@Membership.mem #4 (List _) _ #1 #3, @List.cons _ #2 #1]
Try these:
  [apply] [grind .] for pattern: [@Membership.mem #2 (List _) _ (@List.cons _ #1 #0) #1]
  [apply] [grind! .] for pattern: [@List.cons #2 #1 #0]
Try these:
  [apply] [grind .] for pattern: [@Membership.mem #4 (List _) _ (@List.cons _ #3 #1) #2]
  [apply] [grind
    =>] for pattern: [@Membership.mem #4 (List _) _ #1 #2, @Membership.mem _ (List _) _ (@List.cons _ #3 #1) #2]
  [apply] [grind! =>] for pattern: [@Membership.mem #4 (List _) _ #1 #2, @List.cons _ #3 #1]