If you make a property mandatory then all of the items it applies to should have this property selected.
But if you now try to set the property in an action for a specific item (including the player character for character properties) then the property does not appear in the drop-down list.
You can set it for a referenced character, but when you test it in runner it wont work.
To make it work properly you need to open and re-save every single [character/object] in the game.
Rated high priority because it can be very confusing for anyone who doesn't know what the problem is.
I can confirm that this is still the case in 188.8.131.52. Simply opening and clicking ok to close is enough to 'update' a location, but for larger games this can be rather tedious, and can be seen as counter intuitive regardless.
This other report might be a symptom of the same issue: http://www.adrift.co/bug/18731
I was about to post a similar suggestion. Every new property created, it seems nothing gets updated object/characters and you have to manually do this for each . This would be a nightmare for large projects. Not sure if this would be a problem also when you import a module that has new properties?? Something to be tested when this gets fixed which i hope this will be in the next update :) as its quite a big issue if you cannot add new properties to a game late in the project due to the sheer number of objects/characters etc.
Also this is a problem when deleting properties too- you have to manually update all entities depending if character or object so Dev and Runner doesn't throw a 'property x is missing' error when loading a game or testing it.