I never saw any structured editor on these machines, how did they operate ? grammar guided insertion ?
That was not a very good description so try this: https://www.usebox.net/jjm/notes/basic/ (scroll down for keyboard pic and also some code). Or this video : https://youtu.be/zgjGsNS6a0Y?t=167
10 print "hello world!"
to get a feel for it.