Is there a keyboard shortcut in TeXnicCenter to complete the current environment? In other words, it should add the appropriate
(Summarising comments as an answer, so that this question is 'answered'.)
It seems that you are looking for a keyboard shortcut to take the input
and have TeXniccenter automatically close the environment with
(i.e. to close whatever the last environment opened was.) At present, the answer is 'TeXniceenter does not have such a function'. Perhaps lodge a feature request.