PhD: Online philosophy courses and their worth when transitioning from an unrelated field to philosophy
My guess is this depends on what sort of on-line course it is ...

(1) In the course, you write one or more papers, which are critiqued by them, and at the end they issue some sort of credential to you

(2) You listen to lectures on-line, do assigned reading, and nothing else

Perhaps (1) would be of value in applying.  But not (2).  Of course (2) could still be of value to you, personally.