Ah! Find/replace was what I was gonna ask for next!
About the Undo:
4000 bytes is a little ridiculous for a line.
I have only had one source in my entire coding experience go over 4k, and that's because it consisted of gigantic walls of text. One source! I understand that sources can get a lot bigger, but the point I am trying to make is that, if you have one line that's 4000 bytes long, you really need to rethink your code, even if it's data; one keypress, and thousands of bytes of data are gone. What about halving it? Having half for the undo, and half for the clipboard.
Also, can we please have a button to quit the editor without saving? Or, better yet, have a button that brings up a menu of all the things zStart can do, and one option in that menu is to quit w/o saving.

Instead of the line not being drawn when one part of it is off the screen, the part that is onscreen is drawn.

2296: You are a post stalker

2295: you do so anyway

Ohhhh. It all makes sense now!

Yeong "Bridge" Jin_Cool:
Almost right: It's an ABnormal 4func calculator!

He supports himself

Aha! A bridge joke! Nice!