Learn English – When is ‘what’ used for living beings

This is an interesting syntax, though I've heard it's falling out of favor.

The purpose is to avoid ending a sentence with a preposition (from, to, on, etc). So rather than say

"...the car I am sitting in."

you would say

"...the car in which I am sitting.".

This can be confusing, even for native speakers, so it is becoming less common. I had a linguistics professor who used to say

"A preposition is a fine thing to end a sentence with."

The "preferred" syntax (according to an English professor) would be

"A preposition is a terrible thing with which to end a sentence"

which clearly sounds terrible.

Overall, you can impress people with your knowledge of this fancy syntax, but it often times will be more confusing than illuminating.

This is technically just fine, and in fact is actually the grammatically correct way to say that. You will definitely not be marked down on a test or an academic paper for using between which in that way (in fact you might be applauded).

However, the unfortunate truth is that there are cases where "grammatically correct" and "commonly used" are not the same thing. This is one of those cases.

Despite being correct, saying between which I parked my car will likely sound awkward to most English speakers. Instead, most native speakers would probably say which I parked my car between, even though this is not actually grammatically correct.

So, if you're looking to be correct (for example, in an academic/professional setting) the way you have phrased it is actually the right way to go. If you're speaking more informally, using the incorrect but more common which ... between form will likely sound more natural to most people.