The Stack block is for arranging blocks vertically. You can easily convert a stack to a group or row block.

Stack Block – Documentation – WordPress.org

We have given the stack below a blue background and coloured the pargraphs to make the organisation clear..

A paragraph in a stack block. You can add a series of blocks inside a stack block.

Final paragraph in a stack block.

Document Overview

The Document Overview is a great way to organise, edit & move blocks especially if you have a more complex layout. It is opened from the top tool bar or by typing control-alt-o (^⎇o).