Toolset has an immensely powerful feature, which lets you nest ShortCodes within each other, or inside HTML attributes.
Often however, output breaks due to nesting ShortCodes.
There is a quite often overlooked very simple trick to avoid that.
When inserting a ShortCode, usually its attributes will be wrapped in double quotes like attribute="value"
Now, when nesting a ShortCode in the attribute, like attribute="[shortcode]", and the nested ShortCode also uses attributes, the result would be attribute="[shortcode attribute="value"]"
That will break the output and usually result in a broken front-end.
To avoid that, we can alternate the apostrophes like so attribute="[shortcode attribute='value']"
Similarly, when using nested custom ShortCodes, it is vital to register them in Toolset > Settings > Front End Content > Third-party shortcode arguments.
By doing so, the Toolset ShortCodes engine will add the ShortCode to its “magic” ShortCode parser and make sure these Custom ShortCodes - when nested - are expanded properly.
The Toolset Documentation states that the registering is only required when using these ShortCodes in conditionals, however this is not true. It is also required when nesting Custom ShortCodes in Toolset ShortCodes.
If you happen to nest a Toolset ShortCode inside a Custom ShortCode attribute, make sure to additionally expand the Attribute Value of your ShortCode in the PHP function registering the Custom ShortCode with wpv_do_shortcode( $atts['the-att'] ).
This will make sure that any ShortCode nested in your Custom ShortCode attribute will as well be expanded properly.