There are several different market solutions that allow to organize column bands and arrange them in multiple rows, so that headers and cells can occupy more then one row, like at this image.
I need to create own implementation (or find any opensource solutions for Qt) but I can't find any manifest of how this can be implemented.
Qt does not have the concept of sub-column. You should implement it in your own which can be done by using an item delegate for the specific column. The item delegate could be your custom widget displaying any data you like.
You can also have a look Qt Grid View which enables you to have arbitrary spanning of columns and rows. Just download the source code to get a hint about the implementation.