So finally managed to get the right (well, right-ish) feel for the text editor. The text is edited as a set of 32 pages, each 4kb in size. Pages are saved in the flash chip when switching to another page or powering the device down.

Added some useful functions to the extra buttons by the screen, let's call them "F" keys, if the left ones are F1-F5, and the right F6-F10, F1 now saves the page, F5 goes one page back, F10 goes forward. Pressing F6 three times clears the current page, F7 pressed three times discards the recent edits, and F9 puts the device to sleep _without saving_ so careful with that.

Speaking of sleep, I added some features to the low-level library... starting with the original one by Larry Bank I copied some stuff from the one by fdufnews from the SMART Response XE BASIC, and changed some. Most notably, the power button not only wakes the device up, but also switches it off (hold for 3 seconds) and the device also auto-powers-down after about 6.5 minutes.

Concerning the enter key, at first I put it on the "del" key, which looked like the right place, but in practice, I found myself hitting the "del-now-enter" when trying to delete, not sure why. So I reverted that. Now del is backspace, shift+del is enter, and sym+del is delete. While there I added a bunch of useful characters that weren't assigned to keys including @#^&{}, and I discovered that the funny key, for like, fractions? next to the sym, was "enter" all along. 

In other news: I got some pogo pins for programming the SmartResponseXEs without opening the case (I got a couple, and they are not easy to open). But oops, the pins I got weren't quite optimal. After like 3 attempts to arrange them into a working connector by hand, and missing some contact points, I realized I need more precision, luckily enough my 3d printer was up to the task. The design took some tinkering but worked in the end. I'll include the printable model in the project files.

BTW, I had trouble finding this information on the web, so for future reference, the programming holes are about 2.1mm in diameter, the pitch is about 4.76mm along the row, and 3.8mm in the other axis, and the 2 offset holes are in the middle of their respective boxes.