As a result of ideas born during the 35th Project Week, a new "Apply to all segment checkbox was implemented in the “Margin”, “Hollow”, “Smoothing”, and “Scissors” effects of Slicer’s Segment Editor.
By checking this box, you can initiate easy and quick serial processing of all visible segmentations within a segmentation node.
I created a short video on how to use this with the “Margin” effect in the vertebral body segmentation. Some other videos might follow.
Thank you @lassoan for your help.
The functionality is available in release 4.13.xx (currently preview)