I agree that if you just want to quickly assign the action of a handle button it is currently a bit long winded and can also be confusing for some users.

However, the key profile system does provide a way to quickly switch button actions once they are setup.  Any solution should not replace key profiles but perhaps it could be changed so that if you want to fix a particular action to a playback it is assigned directly rather than having to setup and then select a key profile.  I think there is also scope to rename the entry point menu to minimise confusion.

For example:

• [Playback Options]
• <select playback>
• [Button Action]
• <select button> (or select relevant softkey [Blue]/[Grey] etc.)
• [Key Profiles] (takes you to a sub-menu of available key profiles along with option to [Add])
• [<action 1>]
• [<action 2>]
• [<action 3>]
• etc.

If one of the <action> softkeys is selected it applies directly.

This would give the 4 press solution unless actions are on other pages while retaining key profiles and their benfits.

If any changes are made I think it is important that the Playback Options menu does not span pages.

I would like to see this in addition to key profiles. Key Profiles can be a helpful thing when you got a couple of playbacks you want to change.
One way I can imagine this to work is based on computer games where for certain games you have a few controller presets but can additionally edit the button config freely.
Imagine a drop down with all key profiles saved so far as preset in the same window where you can freely assign the buttons. Also an option to save the current config as a new key profile would be helpful at that point.