The current work around is to assign the custom fields to yourself or another internal user.

The challenge with this is then that assigned employee has to sign every proposal that is sent out, otherwise it will not show the document is signed.

It seems like this might be fixable by not making the employee have to sign (there is only one signature for client)

Or other better solution is to create an option where we can click on custom fields in template document, and there is a toggle that asks "Editable by recipient(s)?"