Level NumberingKeyCreator \ View \ Level \ Overview \ Level-Numbering
Each level has a number associated with it. This number may be zero, indicating that this level has not been assigned a number.
If the level has a number, then that number of each level, and its parents, can be used as a unique identifier within the level’s part. For instance, if level 1 has a sub level 5, which has a sub level 4, then we can uniquely identify that bottom-most level as "Level 1.5.4". Use the right click context menu or left click highlight the level number to change the numbering. You can move or copy entities based on the level number.