Add an extra menu of common tasks- no problem. Add a datalist dropdown of options to a textbox where the options come from another service dynicamlly? - again no bother but usability of the vendor product went up substantially.
Don't laugh but I had more results scripting mouse/keyboard automation on 90s oracle GUIs [0] than the app I mentioned above.
[0] I could prefill half the stuff and help the rest with powershell, it gave me 70% time reduction on most tasks
<flippant-comment-from-a-random-hn-poster-who-doesnt-know-your-circumstances>
The job market's great right now
</flippant-comment-from-a-random-hn-poster-who-doesnt-know-your-circumstances>
Hopefully more usefully as a comment - browsers are super hackable, you might be able to use a javascript bookmarklet to effect some improvements. Something like this https://caiorss.github.io/bookmarklet-maker/ (there are others) makes life easier for creating these.
bookmarklets don't allow for injections into the app so it wont work
Presumably this has to hack around cross-site restrictions nowadays (it's a couple of years since I did any website JavaScript).
1. Clone that repo
2. Run my fake vendor app - in this case an html page with an empty text box - npx http-server
3. Add the browser extension - tested in firefox - then refresh the page
Now you should see the title fields from https://jsonplaceholder.typicode.com/posts in a dropdown that's now been added to the input field of the fake vendor app page.