Add custom sub-header action

I would like to know if it is possible to add a custom global table action which replaces the ‘Add new’ button. In this case, we want to add a ‘Show all’ button, which interacts with another element of the application. I know that adding custom actions is it possible, but for our functionality we need this button at thead level.

Maybe an approach could be to modify the default behaviour of the add action at the settings JSON of the smart table, but we didn’t achieve it.

Global table actions are mentioned at official docs, at section Table Configuration, hideSubHeader property:

Source: Angular Questions