Thank you, I followed something similar to your suggestion, only I did the randomization in a python script outside of calibre before importing. Here's the script I used in case anyone is interested. Basically, the script adds a random prefix to each file name, and then I import them into the book editor, which will now be in the new order determined by the random prefix.
Code:
import os
import random
path = r"path\\to\\folder\\" # note: using double slashes because windows
string_to_draw_from = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"
for file in os.listdir(path):
letters = ''.join(random.choices(string_to_draw_from, k=2)) + '_' # 2 random letters as prefix
os.rename(path+file, f"{path}{letters}{file}")