How do the the main map scene levels work?

[FoozleMcDoozle]

I was looking at the towns and castles on the main map and noticed that the siege equipment placed outside was flagged to be visible at all levels, not just siege, however they only appear when the visibility is set to the siege level. Does the main map do something special with levels? I also saw the sceneleveler script, does that have something to do with it?

 

[NPC99]

I'm only guessing, but I suspect the answer is in this picture:

castle_B6 (entity inspector left) has everything ticked. It's child bat_siege (entity inspector right) doesn't have base ticked, only levels 1 to 3 and siege. I suspect that without base being ticked the siege equipment will only display on the campaign map during a siege.
The sceneleveler script is only set up to create or delete levels 1 to 3 - no mention of siege or civilian. In any event, there's no separate navmesh for siege or civilian levels on the campaign map. So, I doubt those levels mean anything in the worldmap. Especially if my guess is correct and the switches reveal or hide the icons without needing anything more. I believe the siege engines themselves are animated by a separate script
called CampaignMapSiegePrefabEntityCache. However, I could be wrong - only guessing.

EDIT - @NIN3 advised: the "siege layer" is not really used on the main map. Their visibility gets set with another script.

EDIT - TW Documentation update - http://docs.modding.bannerlord.com/editor/scene-editor/level_system/