Tracking sub-topics to a parent topic 4 levels deep and updating all entries from 1 sheet

I've spent a few weeks working on this and have gotten somewhere, but the result is unusable so I'm coming here in hopes of help.

To better keep track of my thoughts, I want to make an excel document that would be the 'master' topic. The master topic would then have subgroups down up to 4 layers deep, each one accessible by a drop down menu.

I set up each dropdown menu on sheet1 to populate its self with selections from sheet2. Based on the selection in dropdown1 in sheet1, column2 in sheet2 would update its self to reflect the subtopics of the dropdown1 selection and let the user pick from those. Likewise dropdown3 updated based on the selection in dropdown2.

I don't need to go all 4 levels deep, as each parent topic still has its own description that gets shown on sheet1 after being retrieved from sheet 2, and when the description on sheet1 is updated the contents is copied back to the originating cell in sheet2.

What I have works in a incredibly cludgy sort of way and takes ~ 30 seconds to update all the fields and make edits and really breaks up the flow of writing out ideas.

Any recommendations for a better way to build this is greatly appreciated and would be a relief.

If I need to post my existing working document & example code for those interested in helping I can do that as well.

Thank you,

If I need to post my existing working document & example code for those interested in helping I can do that as well.

Hmm?
That might be be a good starting point ...

Ok, for whatever reason the sheet was weighing in at 2.7MB, so I had to zip it as attached.

Any insight to this would be really really appreciated.