On Pc or Mac the approach remains similar.
In this example, we want to group Alien, Aliens, and Alien 3 in the same button :
By moving to the first movie and right clicking, you will see the following menu. Choose the option "Add to a group ..."
Select "In a new group...".
By default, it detects a possible group name "Alien - Saga" thanks to its database.
You can change it if you wish.
Then, press OK.
Your group is now created and your movie placed inside the group.
A default group picture is assigned.
A small "G" logo on a red background at the bottom left indicates when a button is a group.
You can customize the name and images of the group.