When to split ruling authorities (especialy for monarchies)?

I've a question, and hope this is the right place to ask, if not, sorry:
In the Norwegian catalough the coins issued under the German occupation, under the second world war, has its own ruling authority. But eg. in the Netherlands, they are just classified under Queen Wilhelmina, but noted as (German occupation).

I kind of understand, why Belgium and Denmark don't have a "German Occupation" ruling authority. Since the king's face or monogram feature on the coin and the kings stayed in the country.
In the Denmark catalough, some of the coins are titeled with (German Occupation) though.

In both Denmark and Belgium, some of the occupational coins/war coinage, was minted a few years after the occupation ended.
A little curriusity though, is the the 2 Francs, from 1944, categorised as (Allied occupation)

So Belgium could have:
Leopold III (1934-1951)
German Occupation (1940-1944)
Allied Occupation (1944)

And Denmark could have:
Christian X (1912-1947)
German Occupation (1940-1945)

In short my question is, when to have a seperate ruling authority for the German Occupation? When the Monarch or other ruler/authority was the same before (under?) and after?

I would suggest that we need "German occupation" as the sole ruling authority when there was a clear break in the monarchy. This would appply in the Netherlands, Luxembourg and Norway, where the monarchs went into exile, but not in Belgium or Denmark, where the monarchs remained during the occupation. For the last two, we could have "German occupation" as a second ruling authority but for the first three, there was a definite break and we really ought to list those three monarchs with dates up to the occupation and starting again after it.

Even though I'm not the one to make the decicion nor implement it, but could you exemplify it? What's your difference between eg. the Danish and Norwegian listing then? I'm not sure I quite understand to be honest.

When Germany invaded Norway, the Netherlands and Luxemburg, the monarchs (Haakon VII, Wilhelmina and Charlotte) went into exile and ceased to be the de facto rulers for the duration of the occupation. Hence, it makes sense to divide these monarchs' reigns into pre- and post-occupation with "German occupation" as the sole ruling authority inbetween. In contrast, the kings of Belgium and Denmark (Leopold III and Christian X) remained in their countries and the kingdoms continued throughout the occupation, hence we could have two ruling authorities for the period of occupation. You can see the difference most clearly on Dutch and Norwegian coins, where all reference to the monarchy disappeared, whilst the kings continue to appear on Belgian and Danish coins. Luxemburg was virtually annexed by Germany and used the Reichsmark, so you won't see any coins or notes at all from there during the occupation.

So like this is in Norway?
Haakon VII (1905-1941 & 1945-1957)
German occupation (1941-1945)
(or instead of one Haakon VII:)
Haakon VII (1945-1957)

And like this in Denmark?
Christian X (1912-1947)
Christian X - German occupation (1940-1945)
Frederik IX (1947-1972)

Or do I miss anything? :)

That's what would be displayed for Denmark. We set it up by having "Christian X (1912-1947)" and "German occupation (1940-1945)" as separate ruling authorities, then selecting both for the appropriate pieces. For Norway, two separate ruling authorities for Haakon VII will work best when displaying by ruling authority.