Custom text separators?

How do I insert a custom text separator? I see that I have the option to insert one, but unless I use something from the keyboard, I can insert a customized one. Is there a way to have it reference another file? (I don’t see a way to upload a file in this field.)

Thanks much!

You can type or paste <$include:binderFileName> in the field.

Thanks Bob! I appreciate the help.