Even though the generators do different things, there are a couple of settings most of them share:
Editing Issues via Generators
When you use the Group, Extend or Sort by Rank generators, by default the structure will be able to update some JIRA data as you move issues in the structure:
If you want to disable this, deselect the Allow changes via Structure checkbox in the generator settings.
The scope of the generators is defined by its position in the structure and the Levels option.
If you place the generator under the top-level root item, the generator will be applied to the whole structure. If you place it under some static item in the structure, the generator will only affect the descendants of this item.
To limit the scope further you can set on which levels the generator should run.
This option is especially useful when you are defining generators for the hierarchy, where on different levels you have different types of relations. For example, the top level and the 2nd are connected with issue links, the 2nd to the 3rd with epic links, and on the 4th level you have sub-tasks.
In this case you will have three generators added under the root of the structure with the following Levels settings: