New User - Actions Panel Question

The metaphor of a folder (action set) makes sense, as far as it goes – it is restricted at one top parent level, one can't insert a "folder" into a "folder", just as one can't drag one file into another file, as files are unique/independent – they are not folders, they are files.

An action set is not a folder, it is a file. The interface uses a folder to display the action set's contents (actions), however, the action set is really a stand alone file with an .atn extension. There may be one or more actions (not action sets) contained within the action set file. 

Knowing the above, you can restructure multiple separate action sets into a single action set, by combining the actions from each action set into a single new action set, as illustrated here:

That being said, depending on how the actions were originally created, one action may refer to another action set and action by explicit name, so restructuring them would break the action at that step.

Actions are in Action sets,  Action Sets can not  contain Action Sets just Actions.   There is no nesting no hierarchy.  Action can Play actions in the same or other Action sets. Actions can not play themselves recursion is not supported.  Every action set could contain an action names Magic.  They could be copies or completely actions. You can organise Action into Actions sets and action sets can be loaded and deleted in the Action Palette,  Therefore you could customize the Action palette for particular task  you would cleat the Action Palette  use the action palette menu item Clear all Action then load the action sets you need load for the task in the order you want  them in the Action Palette. You could probable use the scriptlistener to record a script to automated these setup for the Action palette.  Have different Action Palettes for your different custom workspaces.