How can I access subfolders in Apple Mail on my iPhone 16 Pro Max?

I do not see any way to access Mail subfolders on iPhone 16 Max, but the folders do appear in iCloud.com, iMac, and MacBook Air. I see some comments on Community that there should be a blue down arrow on the iPhone to access the subfolders, but I do not have any blue down arrows.

[Re-Titled by Moderator]

Original Title: Subfolders in iPhone Apple Mail