Screenwriting software is ridiculously constrained. Margin sizes, line sizes, font sizes, font weights, everything, is ridiculously locked down. In the physical world, there were (are?) equally ridiculous constraints on things as minor as the binding of the scripts (which is to be done with brass "brads" ). It's absurd and absolutely intentional because it's what the real, ultimate customers of the screenwriting software want.
The real customers of the screenwriting software are the people who read and ultimately buy the scripts, and they want all these constraints in place. 99.99% of all screenplays never get bought, and 99.9999% of purchased screenplays never make it into theaters as a film . In that sort of environment, the top goal of every screenplay buyer is to avoid wasting their time on screenplays that aren't worth reading.
If you send your genius script to people in Hollywood set in Helvetica or Gil Sans or whatever other font you favor, it will not get read. Period. That's an absolute deal killer for potential buyers. The reasons are a mix of process (constraining margins, font size, line spacing, font keening, etc. makes documents instantly comparable - look at the page count and you know the running time) and sociology (filmmaking is an incredibly complex and expensive multi-player art form with each project involving hundreds of people working together to build a product for millions or hundreds of millions of consumers, and the person considering buying your script wants to know do you understand how that works well enough for your idea to have a chance of surviving).
It's kind of like the way I put a footnote reference in my first paragraph starting with  instead of  or * the way the rest of the world would have if they wanted to put a footnote in plain text like this, it's an early visual cue that I might be a writer who gets how HN works. Ditto for the  footnote around the obviously made up, quantitatively inaccurate but qualitatively accurate stats on screenplays (the WGA does occasionally publish stats on the number of people who earn a "full time salary" writing screenplays and the numbers are amazingly depressingly small).
It doesn't matter how great your idea is, or how unique your personal creative vision is. If you put pictures in your screenplay, you are putting a giant HTML <blink> tag in your script that screams to every serious reader "My screenplay isn't worth your time to read, because I don't know what I'm doing." It's all well and good to be a special snowflake in your own mind, but if you want to be taken seriously in an incredibly sophisticated multi billion dollar industry where >99% of screenwriters never produce a script that gets produced, you distinguish yourself not by showing you know how to use blink tags but by showing you know how to grab people's hearts without them.
If you are a writer and you must have visuals, keep it to a single page, called a one sheet, with a single powerful evocative image on it to help the people you pitch to remember the concept for your story (and then try not to use or show it). Directors are buying your script, not your visuals.
When you're ready to produce and/or direct your own screenplay, then you can assemble your own visuals, but you still want to keep them out of the screenplay. Put them first in a mood board that conveys the feel of the story without the constraints of the script. Then put them in storyboards that convey the visual telling of the story at a high level (initially) to facilitate a deeper conversation with all the parties involved in the effort. Then produce a story reel, communicating the feel and pacing of the story. Or ditch them all and just make the film. The choice is yours if you are a producer/director but it's theirs if you are a writer. This is a big, complex, sophisticated industry you're working in. It's not always going to be optimized for you or your needs because it's optimized for the total needs of the set of all players in the industry.
All of which means please don't put images or blink tags in your screenplays and please don't put image embedding tools in your screenwriting software unless you want the people using your software to fail at their ultimate goal of having their screenplays made into actual films.
 we'll come back to this in a moment
Unfortunately, you come across as highly antagonistic to a screenwriter (a) whose script was almost immediately made into a brilliant, popular film  and (b) whose story was foundationally about the way language affects our thinking.
Your main argument is that people's scripts will get rejected if they don't chain them into a box and use peculiar little brass fasteners to hold them together. This inclines me to believe that you've not yet actually seen "Arrival."
Sometimes I think a little change in the film industry would be productive, if it meant we'd get more movies like "Arrival," even if it means breaking rules, and fewer movies like "Captain America: Civil War," who follow the rules but composite dozens of mismatched absurdities and are basically mass-market children's cartoons.
 Common knowledge. By the way, championing your knowledge of "how HN works" WRT references just sounds self-congratulatory.
The bit about the footnote styles was more to help HN readers who are not screenplay experts validate an example from their world where formatting styles communicate in-group vs out-group status, because as you point out "everyone" knows footnote counters start at 0 on HN.