Your "desired" data structure does not make sense at all. Using heterogeneous lists only complicates access later on. Using a dict of lists of lists may be a bit better but still unnecessary when you can work for example with Workbook/Worksheet objects. What would you do with this data structure? It smells like XY problem to me.
If you can't explain it to a six year old, you don't understand it yourself, Albert Einstein
How to Ask Questions The Smart Way: link and another link
Create MCV example
Debug small programs
How to Ask Questions The Smart Way: link and another link
Create MCV example
Debug small programs