Had me stumped for a little while but I like to move emails I want to keep to certain created folders. The option was there at the bottom on open emails with iOS 12 and isn't on iOS 13.
I looked in Mail settings and set a swipe to the left to include the move option so now moving from an open email is possible.
Just wanted to post this incase any others had this issue.

I looked in Mail settings and set a swipe to the left to include the move option so now moving from an open email is possible.
Just wanted to post this incase any others had this issue.