Can't edit segmentation created from a labelmap outside a box


I created a segmentation from a labelmap. I tried to edit this segmentation using the segment editor but I can’t get outside of a box that seems to be the smallest box around my segmentation

In green you can see the segment from the lablemap in blue I tried to segment as far as possible.
This happened on 5.6.2

I found a workaround where I create a new segmentation and move my segment in the new segmentation but I was wondering if a more elegant solution exists

Yes, you can change the geometry of the segmentation.

Thank you, it worked
As a bonus, here is how to do it in python