Google's John Mueller said it isn't recommended to use // - double slashes - in your URL path. He said generally if browsers can handle it so can Googlebot. But he said on Twitter "// is generally considered a bad practice though, since what it's really saying is "use https"."
Here is John's tweet:
If it works in a browser, it should work for search. "//" is generally considered a bad practice though, since what it's really saying is "use https".
— 🍌 John 🍌 (@JohnMu) September 3, 2020
It is funny, this is a topic we covered all the way back in 2005 where Google was accidentally adding double slashes to your URLs at one point. John Mueller also gave some details on trailing slashes in 2017.
Forum discussion at Twitter.