For just capturing the output of a command, you can use:

r !somecommand

But if you want to filter a range of lines through an external filter with POSIX ed(1), you need some sort of temporary storage (whether a file, the system clipboard, a tmux buffer or whatever). There's no analog to

:10,20! rot13

offered by vi/vim.

Someone (can't find the post/author at the moment) did hack this functionality into ed, but it's a custom fork of POSIX functionality.

Toronto qed (descended from ed in the late 1970s, not the 1960s editor that inspired ed) has three commands for exchanging text with other programs:
>command # send to command's standard input
<command # receive from standard output
|command # send to stdin, read from stdout, replacing original addressed lines

Of course > and | take an address range and < a single address, like w and r.

I use | quite often either in ed or in sam; latter written by the guy from whom I caught the qed bug.

Implementing | takes some thought to avoid deadlock if pipes fill and block. Qed does it by spawing a temporary process to do the writing, while the main process reads into the buffer.

I've just started getting three month refills, hurrah!

Even with that, I would recommend checking the FDA Drug Shortage[1] list about a month before each refill. I've seen various ADHD meds listed there, though not yet the ones prescribed to me.

[1] fda.gov/drugs/drug-safety-and-…