JF Side Buttons - Free Sidebar Buttons module for Joomla! 《JoomForest》
Preview Button - Better Preview - Regular Labs
Ajo Bootstrap button module
Tutorials to Joomla! - Joomla! tutorials and extensions - JoomTut
GitHub - astridx/mod_agiframewrapper: Joomla Modul. This Modul extends the Joomla core Module mod_wrapper. It adds a button, so that the content of the iframe is only loaded, if the button is pressed.
How to preview module position in Joomla templates - ThemeXpert
Displaying a Video Within an Article or Module (Joomla! 3.x)