custom-css-manager-plugin

This plugin works well for me. It enables me to make changes without having to mess with the core CSS files. It does not always work for all the sites I manage but it does the job.

This is one of the plugins that I install on all of the sites that I manage, even ones which have their own CSS option. One nice thing about this plugin, that I’ve not seen with other CSS plugins, is that the stylesheet is read in on the admin dashboard as well, which allows you to style the admin dashboard if needed (make font sizes bigger, hide controls you don’t need or don’t want your other admins to accidentally use). It hasn’t been updated in over three years, but there’s been no need as far as I can tell. It does just one thing very simply, and does it well. If any improvement can be suggested, I would like to see the stylesheet become active on the new Customizer as well.