I would like to know if Doccano can support a hierarchical or layered tagging structure for sub-entries in annotations. Here's my use case:

In medical records, there's a section for the current medical history, and I want to label specific sentences or words within this section as items on a psychological assessment scale for symptoms and disorders. Ideally, I would like to:

1. Select the text, then choose the main category "Psychological Symptoms and Disorders."
2. From there, select a sub-category such as "Assessment Scale."
3. Finally, within "Assessment Scale," select an item under it, which represents the specific sub-entry or sub-category (like individual items/questions on the scale).

This hierarchical approach allows me to tag data in a more granular and organized way, ensuring that each entry is nested under the appropriate category and sub-category. Does Doccano currently support such a feature? If supported, how should I use? If not, can I do so by modifying the source code?

Looking forward to your reply!