If you need more than 6 levels of headings, you might want an outliner
When writing documents, it can be useful to organise it into a hierachy of headings. Most document writing software allow around 4–6 levels of headings.
Some people have expressed that this does not give them enough levels of hierarchy. If that is the case, it is in my view that person requires either additional structure, or a different structure entirely. That could be the use of Outlines.
An Outliner is a different tool from a document writer entirely. Where a document is fixed at up to 6 levels of headings, an Outliner allows unlimited levels of indentation, at the expense of formatting options and also an arguably ugly publishing format.
My outliner of choice is Logseq. Some alternatives are Roam Research and Tana.