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? 

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.

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!