Idea Summary
Allow the File Upload page item to use substitutions for the size. I went to application definition and added MAX_FILE_SIZE as my substitution string, but then when I went to type in &MAX_FILE_SIZE. into the Maximum File Size (under Storage) it wouldn't let me.

Use Case
I have multiple places within my application where a file can be uploaded. Best practice is to restrict the size, but I don't want to have to type in an Integer in multiple page item Maximum File Size attributes.