Module to manage submodules
There's no such concept as parent and sub/child-modules in Drupal. You'd have to define what you consider to be the parent-child relationship, pick what physical properties of the module you're going to use to describe that relationship, and code a solution from there.

Drupal's own native mechanism for grouping modules is using the package key in the module .info file. In the case of Actions Permissions, for example, the package is defined as "Administration", so you can find it under the "Administration" fieldset, grouped with other modules that are considered to have (loosely) related functionality by their respective authors.

On a slightly un-related note, but you can improve the UI of the modules page using Module Filter if it's becoming unwieldy.