Notify Slack channels on subitems changes

Hey Monday users!
I’ve been trying to create notifications on Slack whenever a subitem status is changed.
First, I created a dependency column that will allow me to have a workflow of the tasks → Basically defined that when a subtask is “Done” then the next one should change to “Next Task”.
But then when I want to notify the Slack channel that one subtask is completed and share what’s the next subtask and the owner of it, it provides me only with task auto populated fields and not with subtask fields.
Does anyone have this issue before? What can I do with it?