Collapsible Groups (or Folders) allow you to create hidden sections on your page with as many links as you wish, that can be opened when your visitors click/tap on the title of the section.
To get started, make sure you already have some Groups. If you don't, create and populate groups following this guide.
Once you have your groups running, head to the Groups Management page, locate the group you want to make collapsible and click on the second icon, as shown below.
A Modal window will pop-up and you can use the switch to turn the Collapsible feature On, as shown below
Once done the group will appear as closed by default
And your visitors can click on the title to show the content