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Whatever time you add, a measure or a quarter note, will obviously and inevitably add to the length of the song and move everything forward respectively. How could it be any other way?? Adding "ghost-time" is not possible.
The only option is to silence a part of the song, which of course, is another thing.
I don't know the details in this case, but maybe bouncing the soft synth to audio could do the trick? Then you could split the audio clip where you want, and after the pause it would continue where it ended.