https://www.youtube.com/watch?v=Ta-5fJQcB5w

Grouping units is nothing more than binding a shortcut to select units. We select a unit using two keyboard shortcuts:

• Shift + 1-0, we add a unit to a given group
• Ctrl + 1-0, we overwrite the data of the unit assigned to the group

It would be good to also abandon the groups we have somewhere in the GUI.