I very clearly remember using typewriters that could adjust the horizontal spacing, aka kerning, between letters. It was possible in the 70’s to scrunch up letters horizontally so as to fit more text in a given area. As I recall—keep in mind this was a long time ago—there was a key on some of the electric models that would allow a person to slightly increment left or right. It was even possible, although difficult, to change kerning manually on all typewriters. You simply loosened the platen and manually tweaked the paper however you wanted it.
Or, slightly depress the backspace key.
I worked on IBM selectrics and Wang processors. That was not available. Why would you even do it? Even if you could, you’re only typing out a redundant form?
You’re right. I often did this while in college and law school with a manual backspace button to add an extra letter to a word that needed to be corected. I’d just push the botton partly down to move the carriage back part of a space, allowing me to insert the new letter, an old typist’s trick with either a manual typewriter or an SCM electric with a manual carriage return.