With @sam’s new Theme system (which is awesome!), is there any way to have site-wide customisations to do things like add buttons to the top menu? These things shouldn’t be tied to a specific theme, and copying them into each of the available themes isn’t ideal.
Also, is there any functionality for multiple css/html customisations that can be enabled/disabled at will? Or is it just 1 customisation per theme? If the latter, what happens when I update my discourse instance that currently has a number of customisations? Will they be lost?