How to compile multiple multi-seq in a list and pick randomly from the list?

[xw6497]

For example, there are 4 multi-seqs and each of them has 5 rows. I need to make a bigger list of 20 rows and be able to pick randomly from them (nth lisp maybe?)

[haddad]

Maybe something like this:

Best
K

[xw6497]

Thank you so much!