Hey, thanks for reaching out again & sorry for my super-delayed reply! Won't happen again!
As for your inquiry — well, since this button is only appearing to the admins of the blog and not to the readers/visitors as well, we don't find it quite that important to make it customizable. We are currently focusing on problems that more oriented to the end-user, which are the readers/visitors.
Hope you understand the position we're in, but we have some more important task ahead of us.
But please do let me know if I could be of any other help, since we always like to hear your feedback. We truly appreciate it!
Take care & have a nice weekend ahead!