Bumbershoot Software

It's funny that you mention the scrolling, also mentioned here: https://bumbershootsoft.wordpress.com/2017/06/04/kicking-off-project-mehitabel/

The Acorn-type CLI is interesting (in my view), and I never realised why until I started using a PC rather than the BBC Micro: there's no shell. The idea doesn't even really exist. The fundamental system call (the OS_CLI SWI on RISC-OS, OSCLI entry point on the BBC Micro) takes an entire command line string, and do whatever that says to do. It's like the shell is permanently there. You never need to parse the string.

This is actually pretty useful, because it means that for a lot of stuff you can simply defer to the OS. No need for interfaces to select filing system, choose floppy disk/hard disk, change directory, tweak key repeat rates, print disk catalogue, etc. - there are CLI commands for all of these, and more, so a program need only provide a way to enter a command to be subsequently executed by the permanently resident CLI. And as the program calls it, any commands so entered affect its state rather than being discarded on exit.

The average file load/save UI on the BBC Micro was that you entered a file name. All the other stuff you might want to do first (select filing system, choose disk type, select drive, change current directory, check file exists or not, etc.) would be done by executing CLI commands via the program's interface for submitting such things. Feels like RISC-OS's unusual drag'n'drop file save mechanic stems…