You can tell unreal to display units in the editor, under the Project Settings > Editor > Appearance:
[/Script/UnrealEd.EditorProjectAppearanceSettings]
bDisplayUnits=True
How do I annotate a visible UPROPERTY in C++:
UPROPERTY(VisibleAnywhere, ThisIsInCentimeters???)
double SwordLength;
so that it will display the correct unit in the editor? (I tried to track down an example, but I don’t know what to search for.)