Question about Raspberry Pi 4 4G Basic Kit incl. HDMI + 16GB SD

Unfortunately, this is the case and it surprised me, but the lid can only be put on and does not lock into place. The 1 mm gap also seems to be desired (possibly for ventilation/cooling).
The idea is probably that it will be removed again and again during tinkering.

I think here the answer is that putting it on is enough.