Classic Editor

Here are the best Classic Editor Addons

TinyMCE Advanced– adds customizable buttons and convenient navigation bar – must have for newbies thru to WP Pros
Black Studio TinyMCE Widget – enables using TinyMCE to edit WP widgets. If you have a lot of sidebar widgets, this is the tool to use.
Widget Content Blocks – more widget block editing capabilities; not as many features as Black Studio with add-ons
Genesis Columns Advanced – Okay WP Pros and newbies wanting to have  column layouts – here is your tool. Warning: shortcodes are sprawling.
Advanced WP Columns – intuitive creation of columns in  Classic Editor; another solid multi-columns choice
Best WordPress Editor – this is special for WP Pros, more buttons – Font Awesome, Bootstrap 3.3.7, CSS Templates, and more
Central Color Palette – must-have enhanced color palette for newbies to WP Pros. Many customization options.
DigiWidgetsImage Editor – how would you like to edit your images within WordPress Media Library directly with layers, type and effects?
WP Editor – extends both Visual and text editor  with added features but has not been updated in 3 years
Zedity – this is a must try Classic Editor addon that delivers effective 3D graphic design to WordPress not available in Gutenberg or top PageBuilders

Other Addons worth trying: 
Kv TinyMCE Editor Add Fonts, WYM Editor – Semi WYSIWYG, TinyMCE Visual Blocks, Frontend text Customiser, FolioPress – watch for plugin conflict,
Content Blocks for CPT, Custom Field Suite