How do I create a directory on remote host if it doesn’t exist without ssh-ing in?

You can use rsync.

For example,

rsync -ave ssh fileToCopy ssh.myhost.net:/some/nonExisting/dirToCopyTO

Note about rsync:

rsync is utility software and network protocol for Unix which synchronizes files and directories from one location to another. It minimizes data transfer sizes by using delta encoding when appropriate using the rsync algorithm which is faster than other tools.