This only works if the sequences are guaranteed to never end with a long knock. If you meant to say the pause goes before the long knock, like in the example you gave, not after it, then it only works if the sequence is guaranteed to never begin with a long knock.

Putting the pause before the long knock instead of after is so counter-intuitive that my brain struggles to allow me to actually tap the sequences that way while I read them, for example your "Tak, tak. Tak." intuitively sounds like dot dash dot (super sister meeting), and not dot dot dash (come here).

I think the scene in that movie is a Hollywood inaccuracy. Tapping/knocking has its own system for communication: https://en.m.wikipedia.org/wiki/Tap_code

dots have no pause after nock, while dash requires pause

That's exactly what I thought. But when the only dash is at the end of the message, how do you tell? ..- and ... are going to be indistinguishable, no?

For a danish, your onomatopoeia choice for a knock would sound annoyingly polite.