How to customize/add logic in Strapi CMS Relation-Ship

Hello developers.

I need your help in Strapi CMS.
my case is simple.

Here i made on collection type. that is called Center and next one is post.

here Center has many Posts relation.

all centers title

• ind_chennai
• ind_goa
• ksi_mumbai

some post content_title

• POST 1
• POST 2

When I add/edit a post, I want to show only any center title starting with ind_ in the dropdown.

My problem is if I have to write the logic for this, where do I write it? if you know that way please tell me guys.

Details:

• strapi v4
• sqlite / psql