How to edit (not add) a child record connected to a parent table from a table component displaying parent table records

So this is my case:
I have a data table, “candidates”. This has become a very long table with many fields.
When the candidate will be hired, there are many things which need to be done, like getting documents, getting candidate data, and so on.
So I created a checklist for the hiring process. This is maintained in a data table, “Checklist”, connected to the parent (candidates) data table.

I have a table component with candidates which are in the process of hiring. What I would like to do is that I have an edit form (not an add-form) to edit this checklist. This edit form should be opened from a button in this table component (action button, or a linked page button, preferably in a pop-up).

Adding a checklist to the candidate is easy. But for editing an already existing checklist, I did not find a solution.

Anyone any ideas?

P.S. there is a solution which is integrating the checklist in the parent table, but this is not what I would like to do, as 1) I only need a child record (checklist) if the candidate is not rejected in the recruitment process and 2) I do not want to increase the fields for a record in the parent (candidates) table even further.