Answer:
Each nodal support has a local axis system X', Y', and Z'. By default, it is oriented parallel to the global axes X, Y, and Z. The "User-defined axis system" option allows you to rotate the local axis system of the support (Image 01).
If you want to align the nodal support perpendicularly to a line, you can use the "Same as line" option (Image 02). The "Same as line" option is only available for straight lines. The local axis system of the support is aligned parallel to the local axis system of the line. The local axis system of the line can be displayed in Project Navigator - Display using Model → Lines → Line Axis Systems x,y,z (Image 03). The axis system of the line can be influenced by the line direction and line rotation. To change the line direction, right-click the line and select the "Reverse Line Orientation" option in the shortcut menu (Image 04). The line rotation can be set in the "Rotation" tab of the "Edit Line" dialog box (Image 05).
As an alternative, you can determine the orientation of the axis system of the nodal support by using a user-defined coordinate system or by specifying three nodes perpendicular to the line.
The three options are shown in the video. For orientation of the support axis system using a user-defined coordinate system or the specification of three points, an auxiliary straight line is created perpendicular to the line. Thus, it is easily possible to align the axis perpendicular to the line.