Add Child Record, then edit that child record, then redirect to edit form of child record

I feel like this should be easy but I'm drawing a blank. I have a situation where, when a child record (media) gets created via button, the user has to save the record after making their changes, then edit it again to update 1 last field. This is because that last field needs to be populated with a location path that contains the record ID of the child media record, which doesn't exist yet when they click the button to add the media. So it just creates a few extra clicks that shouldn't really be necessary. 
So I'm trying to tweak the button to create the media from the parent (request), then edit that same media record by populating a text field with "some string" & the newly created RID for this child media record. Lastly, after adding & editing the record, I'll have it redirect to the edit form of the media so the user can make their edits as necessary.

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Harrison Smith
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