How to reset plugin settings to default?

Question

WordPress

Hello. On Wordpress 4.9.7 - there is a menu plugin "Mega Main Menu v20.1.2" - menu.megamain.com
Problem: I need to demolish all of its saved settings to a clean slate. However, there is no way to do this.
What have you been doing? Deactivated/activated. Basically uninstalled and reinstalled. Still doesn't help. The previous settings are saved.
There is no button in the plugin interface - to Default.
I understand that some plugin files are stored in the site folder on the hosting. They need to be found and removed. But still I can't find it.
The plugin itself has been attached to the Wordpress theme from the beginning.
There is a base plugin file (from the theme). I also tried to install it. But the data/settings are not demolished from scratch.
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QUESTION: how can you demolish the plugin settings in this situation and install it from scratch?

Answer 1

The problem is solved - by purchasing a new version of Mega Main Menu. 16 USD.

Answer 2

The plugin stores data not in a file but in a database. You can try searching for the data manually and delete it, or maybe try a database cleanup plugin like WP-DBManager etc.