On site review CLOSE VOTES everyday we deal with a lo-ooo-t of Third Party plugin/theme/product-specific questions. Most of the questions are closed because they are not in the scope of WordPress.
What we are doing: we are welcoming questions with a nice FAQ page, in my observation, that, nobody reads - like a software license agreement - read or not, agree - here, read or not, post the question.
We can simply pose a dismissible banner/notice before the Question Editor (after question title) notifying the user: not saying what to do, but saying what to avoid. In my opinion the best would be our first Close Voting criteria:
Your question should be specific to WordPress. Generic PHP/JS/SQL/HTML/CSS questions might be better asked at Stack Overflow or another appropriate Stack Exchange network site. Third party plugins and themes are off topic, they are better asked about at their developers' support routes.
But the notice need to be too precise, so the best fit can be:
Just need a simple tweak with the first bullet:
- Anything not directly related to WordPress
- Question on third party plugin or theme (i.e. WooCommerce, bbPress, Avada etc.)? - Please don't
(It's just a demo on screenshots. It can be far better to fit the visual ease)
Note, the green and red bullets are important because they are visually warning the users on the first look.
A notice like this can cut out most of the Off-topic questions on the first row. As this notice will be dismissible, so the user won't feel bothered.
- It can be targeted to anybody from non-logged-in users to someone with a reputation lower to 100 - a must.
- Anybody upper than that, up to 500/1000, will be notified on each new session.
- Users with reputation 1000 won't ever be notified.
If we can trial it for at least a month, I can bet we can cut-off the Off-Topic questions to at least a half.