Attach all child records to parent record

Hi

(the following uses fictitious data in the screencaps)

Here is what I am trying to do and where I am stuck:

I have a custom parent record called 'Allowance'

This has a subtab called 'time import'

The time imports that I am wanting to add to the parent allowance record are also custom records.

Currently, this is what the subtab 'time imports' looks like

I am manually adding the time import child records to the parent allowance record by selecting from the time import drop down and clicking the 'attach' button.

Is there a way to automatically add all child records, meeting a certain criteria for example, to the parent record?