Customization of Del was requested on the ML . The trick is to assign an action to "Delete Content" (thanks Piet for finding this) though it would be more transparent for the user when Del itself has a clear assignment in the first place (apparently to this command).
Heiko, could you write your suggestion in detail?
(In reply to Roman Kuznetsov from comment #1)
> Heiko, could you write your suggestion in detail?
Please elaborate it a bit more...
Moving to NEW...
We need an UNO command in order to allow customization. More info in the referenced post to the mailing list.
Created attachment 168841 [details]
Delete Contents command in the Customize dialog in current master
This command exists, and it is assigned the Delete key on the generic application level since forever (okay, only checked LO 6.0.7 right now):
officecfg/registry/data/org/openoffice/Office/UI/GenericCommands.xcu: <node oor:name=".uno:Delete" oor:op="replace">
officecfg/registry/data/org/openoffice/Office/UI/GenericCommands.xcu- <prop oor:name="Label" oor:type="xs:string">
officecfg/registry/data/org/openoffice/Office/UI/GenericCommands.xcu- <value xml:lang="en-US">Delete C~ontents...</value>
It's just not very easy to find it, like finding any other command in our jungle of commands.
I think this is basically NAB.
Maybe a bit more documentation could be useful on the top right radio buttons in this dialog.
(In reply to Gabor Kelemen from comment #4)
> This command exists...
But the key is still hard-coded, or am I wrong? Guess the UNO command comes in addition.
(In reply to Heiko Tietze from comment #5)
> (In reply to Gabor Kelemen from comment #4)
> > This command exists...
> But the key is still hard-coded, or am I wrong? Guess the UNO command comes
> in addition.
I think the uno:Delete command has the Delete key assigned to it via Accelerators.xcu:
So it's possible to change it in the Keyboard dialog, like OP asked on the Users ML.
Changing the global shortcut of Delete Contents to (just for an example) Shift+Ctrl+D and unassigning the existing Writer-level command of Shift+Ctrl+D works as expected.
This covers the editors, but not all dialogs, side bars (Gallery comes to mind) etc where it is explicitly handled by code. That was not asked for though, as far as I understand.
All in all: feature wise -> NAB; but documentation (extended/normal tooltip) could be more detailed.
Also the option to switch between generic shortcuts and application-specific ones (selected by default) could be made more prominent after an upcoming redesign of the whole tab (bug #115527 - also see similar requests bug # 83548 and bug #66298).
Currently the extended help says: "Displays shortcut keys that are common to all %PRODUCTNAME applications." 
while there is no default tooltip - setting something for that sounds actionable for the short term.