One can customize keyboard shortcuts in "File - Options - Keyboard Shortcuts", but unfortunately this command is not listed there and therefore you cannot assign a shortcut to it. 

About your use case: couldn't you simply lock this segment?

I even think I can just confirm blank segments. A red cross appears in this case, but it does not impede file generation. And nothing is added to the TM.

Do you think this could be a solution, Walter? 

I even think I can just confirm blank segments. A red cross appears in this case, but it does not impede file generation. And nothing is added to the TM.

Do you think this could be a solution, Walter? 

Confirming without any target text is not recommended because you will get verification errors and if you work on a Studio package where verification has been enforced, you may have a problem. 
However, if you lock the segment after having confirmed it with an empty target, the error will disappear. It then looks, like this:

and you won't see any text in your target for this segment.

Very true, Walter!

We´d better avoid error messages, since they may give us unpredictable problems:).

With the shortcut keys plugin suggested by Paul the status-changing task can be done even quicker.

However, such segments are quite rare, so this solution is perfect: leave target segment blank, change status to translated and lock. Nothing is added to the TM, blank space appears in the generated document! That easy! 

Thanks , Walter!