Inserting Mysql queries into array using wp_list_table class

I think you should rethink if creating a custom wp_list_table & stuff is the way to go.

I can tell from experience wp_list_table isn’t fun to work with.

Besides I think (as far as I can judge here) a custom post type (or multiple) would be the way to go for you.
This way you probably don’t need queries.

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