The File Filesystem (2021)

Daniel Stenberg, of cURL fame, co-write an Amiga-editor called FrexxEd where the open buffers were exposed as files in the filesystem.

Meaning you could write any shell script to manipulate an open buffer (not that important as it also exposed all editor functionality both via IPC via Arexx and via FPL - a C-like scripting language), and that you could e.g. compile without saving (that was very helpful on a system where a lot of people might only even have a single floppy drive, and where being able to have the compiler in the drive and compile straight from the in-memory version in RAM so you didn't have to keep swapping floppies was highly useful (just remember to save before actually trying to run the program - no memory protection...)

Classic MacOS in the 80s had "MPW" macintosh programmers workshop - that treated open text windows as files and selections within the windows as files, so it wasn't uncommon to have a portion of an otherwise documentation file have a "click here and hit enter", which would use the selected text as stdin for some semi-ported unix tool. (no memory protection or multitasking, so true pipelines with backpressure didn't work)

BBEdit has something akin - you can select text and run a Unix command on the selection via temp files. Very useful

I want a webbrowser that does that, lets me shell-cd into each tab as a directory