Looking to simplify a form I fill out regularly that doesn't accept auto-fill. I need to pass information from a page to another site's form fields. Won't need to automate the submit because the page has a captcha.
The captcha may render it not possible, unless it can be called by a separate URL. If it can, you simply create a form on your site, simply copy the form along with the captcha URL to your site and change any URLs such as the action and captcha URL from relative to absolute, pointing to their URL and remove any autocomplete="off".
If the captcha is handled server-side so that it only loads for that form, you may be able to fetch the whole form with ajax and just include the captcha, but it could be smart enough to avoid that.
Also, I want to be clear that this solution is meant to work with the captcha and that I am against form-robots that pollute the web. I am also against autofill=off in 90% of the contexts it's implemented, as it should be reserved for login forms that are often public (such as library and university login pages) or absolutely can't allow the data to be stored locally (such as sites requesting SS#). In all other cases, it simply makes the site admins feel more secure while end users come up with either dumb workarounds like storing their credentials in a location less safe than their browser's password manager (like a txt file) or clever solutions like writing their own form or using GreaseMonkey.