Maybe not the most convenient method, but it would be easier to implement a Move up/Move down right-click action. If it works with multi-select (in Segmentations module) then it would be probably usable enough.

I like the idea.

1. It wouldn't make the UI even more complex
2. It would take very little time to implement

It would take very little time to implement

Is it something that could be done for the coming release ?

And would the order be saved with the nrrd segmentation file ? I guess that would the order of segment in the metadata ?

The segments are saved in the NRRD in their order, so yes, it would be different.

I'll try to squeeze this in during the following week. What's the date I should be done with this in order for it to be in 4.10?

I'll try to squeeze this in during the following week.

We planning for the end of the week. But there are few important issue that would be nice to address before effectively releasing. A discourse topic will posted shortly

What's the date I should be done with this in order for it to be in 4.10?

Next few days.

I am re-targeting this issue for 4.11.0. If you happen to address this on time, we will just select the correct "Fixed in Version" field.

Feature added in https://github.com/Slicer/Slicer/commit/f6e71a71b01057465c9c5600c1b72fdca313bdfa