Okay, down to really tiny details:
What would you say to THE EMPTY STREAM to match SICP? When I (wearing my naive user hat) see EMPTY STREAM, I try to parse the "empty" as a verb.
The RATIONALS stream is meant to be a stream of (unique) numbers, not a stream of pairs of integers. So I rewrote
and added the helper GCD function. You might consider whether this complexity is worth it, compared with writing a POSITIVE RATIONALS helper and then at top level just interleaving its result with the negatives of its result. Also, I had to display 200 items to convince myself that it would eventually get around to numbers whose numerator and denominator are both big enough to be interesting. I think it's okay to display a list that you have to scroll through. Alternatively, leave out the negative ones altogether. (We don't show negative integers!) But still show 100 items.
I also edited the comments to remove "(theoretically)" from the descriptions. You have to believe in abstractions! Every single integer (prime, rational) is in there, if you go far enough down.
I also edited the initial comment, because seeing
︎ by itself made me think you wanted me to click on the arrowhead of some block, and seeing "and now, to continue" brought to mind the common use of "and now, the stars of the show, the Beatles!"
Something I didn't do, but want to suggest, is making ONES, INTS, etc., global variables (which I think is doable in v10 without using the variables library?) so that after running the demo, the user can use those, especially ONES and INTS, to create additional streams. ("Okay, class, now make the stream of all the integers, positive and negative included." Or "the even integers," and so on.)
Maybe add a demo of getting the first five items of a huge list after sorting?
...with the comment saying the rest of the sorting isn't computed.
Speaking of v10, I'm happy with your ordering of blocks in the palette, except that I think UNIQUES should move down two (or three, your choice) places. The HOFs are super important!
I still want to do more editing of help screens and demos in the block editor. Do you want to read my changes as I do them?