Actually, I used a full pathname - I wrote "File\ Name" for brevity. In my case (in bash under Linux) no matter what I do, the presence of an embedded space in a full pathname elicits an error from restic - i.e. for a line containing
--exclude="/home/xyz//File Name"
restic complains as follows:
error for exclude pattern: Match: syntax error in pattern
I get the same with "/home/xyz/File\ Name" and "/home/xyz/File\\ Name"