<multiple> groups assigned to one button?

Hello All,
On my network I have a button that control two lighting groups.
When I have scanned my network and look at this switch, it shows up in toolkit as <multiple> as below.
I have read through old posts and also the help guide but cannot see this mentioned anywhere.
Would love if someone could advise how a <multiple> group can be setup?

 

It's setup via the blocks tab on the the switch which allows you to control multiple groups by one key - Add the groups to the "block assignment" columns, and then select which key to control them by

 

Thanks, thats very easy once you know where to look!