When I mark a directory with
mf, then use
mc to copy into the target directory, it copies the contents only rather than the directory itself. I know I could make a new directory with
d, then copy the files into it, but I'd rather clone the directory in one step if possible.
Short answer: no
Long answer: This discussion netrw copy commands clearly states, how this is accomplished with netrw (the target directory needs to be created first).
It is also lamented, that this is easier to achieve in NerdTree. ( m + c according to this answer ...duplicate ...entire folder...).
The above mentioned
dir-diff allows to sync directories.