You travel several countries with one backpack. Some of them restrict drones, some do not. You are NOT going to fly in the country where drones are illegal, but you want to take it with you to another country and fly there, where drones are legal. Will it help to temporarily disassemble the drone, propellers, maybe legs, for the custom check?
The term that you are looking for is called Customs Transit. Mostly done in a form of a Customs Seal applied in the country of origin and checked by the customs of the country in transit during transport to a country where it is allowed and where it is then unsealed.
Not common for individual travel in most cases, but a legal method to transport an object through a third country in transit.
It would probably be better to ship the drone using this method with a Poste restante service as address.
Such methods are an everyday affair for transport firms. Many are authorized by customs authorities to seal such containers (called: Trader sealing).
Precondition is, of course, that the object is allowed for transport in the sending and receiving countries and not on an absolute forbidden list of the country of transit.
Starting 2021 all goods transports from or to Ireland through the United Kingdom will use such methods.