How to check wishlist for region lock?

Just ask the guy you're buying from before actually trading something?

Or just browsing steamtrades would be an idea. Usually what is offered there in the topic title is not region locked (unless they say so).

I don't think there's any way for you check it all in one go.

using the website you've linked, you might be able to submit the form by adding the parameters as part of the url.

if that works, you could automate the process with a Javascript that you execute in the browser's console with your wishlist open (parse wishlist, build url, submit form, parse response).

I had a parrot like this. Its dead now. All of them.