The Evernote database uses a Tag table to store information for Tag records
There are fields for: Tag Id
Tag Name
Parent Tag Id
In the screenshot from my Mac
Tag 3 is a "parent" of Tag 4
Tag 4 is a "child" of Tag 3
>>Is there a way to use tags a visual parent-child hierarchy ?
The screenshot shows the visual tag hierarchy
Tags 1,2,3,4 can be seen in visually
>>If I missed something about how to use tags please do elighten me
You mentioned being limited to Stacks and Notebooks
Notebooks and Tags are fields in the Notebook record
For organization purposes, simply assign a tag to a note
As a bonus, multiple tags can be assigned