The options for how this might be implemented:

• Passing string as URL parameter (GET request) is problematic, as URLs have length limitation that is too short for complicated optics experiment setups (Galilean Telescope config has >7000 characters, URLs should be below 2000 characters)
• POST request allows for unlimited characters; however, if Maroon is hosted on another server, CORS might be a problem; and we'd need some server-side code PHP, node.js, flask etc.; also, if two users access the website at the same time, they must not interfere with each other, so we'd need some solution for this, like session data
• Storing value as cookie/localStorage/SessionStorage would also be possible, but then we'd have to think about different things like cookie consent banners, clearing the cookie again; and Cross-origin limitations also apply here
• some sort of cross-origin communication mechanism with iframe, but both website would need to be open at the same time, and probably also not an elegant solution
• URL fragment/hash, instead of the regular GET parameters, we could send the data as URL fragments (after an # at the end of an URL, usually this is used to link to a certain part of a page like so), Chrome limits these to 2MB (Galilean Telescope e.g. has 8kB, or a bit over 7000 characters), and other browsers might also have limitations of about 80000 characters, but it should still suffice I think, some browsers also only limit the number of characters the URL bar can display but will still process all characters , the server wouldn't be aware of the data transmitted, but it doesn't need to be anyway, so I think this would be the best/easiest solution as of now, feel free to let me know your thoughts