You can nest tabs by giving the nested tab set extra names/ids.
To create nested sets, give the tabs of the nested set an extra name or id, like:
{tab-whatever}...{/tabs-whatever}
Don't forget to close each tab set with a closing tag using the same extra id (in this example: {/tabs-whatever}). If you don't close every set, you will get unwanted results.
Example
Lorem ipsum dolor sit amet, consectetuer adipiscing elit.
Example Tab 1
Aenean commodo ligula eget dolor. Aenean massa.
Sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus.
Example Tab 2
Aenean leo ligula, porttitor eu, consequat vitae, eleifend ac, enim.
Aliquam lorem ante, dapibus in, viverra quis, feugiat a, tellus.
Phasellus viverra nulla ut metus varius laoreet.
Quisque rutrum.
Etiam rhoncus.
Maecenas tempus, tellus eget condimentum rhoncus, sem quam semper libero, sit amet adipiscing sem neque sed ipsum.
Nam quam nunc, blandit vel, luctus pulvinar, hendrerit id, lorem.
Syntax
Indentation in example code is just for clarity. You should not indent your tags and text.
{tab title="Example"}
[TEXT]
{tab-ex title="Example Tab 1"}
[TEXT]
{tab-ex_sub1 title="Example Tab 1.1"}
{tab-ex_sub1_sub1 title="Example Tab 1.1.1"}
[TEXT]
{tab-ex_sub1_sub1 title="Example Tab 1.1.2"}
[TEXT]
{tab-ex_sub1_sub1 title="Example Tab 1.1.3"}
[TEXT]
{/tabs-ex_sub1_sub1}
{tab-ex_sub1 title="Example Tab 1.2"}
[TEXT]
{/tabs-ex_sub1}
{tab-ex title="Example Tab 2"}
[TEXT]
{tab-ex_sub2 title="Example Tab 2.1"}
[TEXT]
{tab-ex_sub2 title="Example Tab 2.2"}
[TEXT]
{/tabs-ex_sub2}
[TEXT]
{/tabs-ex}
{/tabs}