Simple module that re-styles all checkboxes in the admin as Toggle fields (thanks to https://www.w3schools.com/howto/howto_css_switch.asp for the base CSS to make this work)
NOTE: As SilverStripe 4 uses react to generate checkboxes, as of 1.1.* this module utilises a JavaScript mutator to detect changes to the DOM and then restructure checkbox elements based in order to style them (rather than utilising templates).
Install using composer: composer require i-lateral/silverstripe-admin-toggle-checkbox
Just install the module and flush the cache. All Checkbox fields in the CMS will be automatically re-styled