Gadget export
To export the dark-mode-toggle-pagestyles gadget, click on "Download" button, save the downloaded file, go to Special:Import on the destination wiki and upload it. Then add the following to MediaWiki:Gadgets-definition page:
* dark-mode-toggle-pagestyles [hidden |skins=vector, vector-2022, minerva, monobook] |dark-mode-toggle-pagestyles.css
You must have appropriate permissions on the destination wiki (including the right to edit system messages) and import from file uploads must be enabled.