Long ago, working with MS Excel, I frequently used a feature whereby you could outline a range of cells that contained no numeric values, and opt to outline the range MANUALLY, with buttons to “promote” or “demote” individual rows, and other buttons to hide or display various levels of your outlined information. This was especially helpful in creating Tables of Contents which could be modified instantaneously to hide lower-tier data, or reveal every row/column.
I haven’t had a need to use this feature since I retired 12 years ago. Now I’m working on a community project where such a flexible ToC would be valuable. Does anyone know if such a feature exists in LibreOffice Calc