What is another way I could say: “this topic is close to my heart.”
Give some ideas below.

- this topic is dear to me

- this topic makes me feel

- this topic is dear to my soul

This matter is one that I always cared about.

The matter is very important to me and my past

This topic is something I strongly believe in.

I hold true to this topic.

Explanation:

Here are some ideas. You can mix them together and mess around with it to find one you like. I don't know what exactly this is about the I don't have something absolutely perfect for you.

  this riddles' answer is library.

  the "leaves" are a reference to the books' pages that the library contains; the branches are a network of libraries that connect multiple libraries' collections, resources, and items in a system of a common database, integrating them; the branches' organization are a useful management tool for coordinating the multiple collections many libraries have.