In this dialog box, you can create building parts, remove building parts, and assign the desired levels to building parts.
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Table
Click on 
Add new building part or click in an empty row of the table to create a new building part.
Table context menu
Right-click in the table to open the context menu for inserting and deleting building parts:
Name
Specifies the name of the building part.
Levels
The select button opens a list of levels contained in the project. Select the levels that belong to the respective building part.