On my client's site, there will be quite a few widgetised areas - one for each page created plus global ones. The problem is that they all display in the "widgets" section in theme customizer at the same time, making managing them very problematic.
For example, let's say that the client is in the customizer and is viewing the homepage. On this page, there are 2 dynamic sidebars (specific for this page) and 1 global sidebar (in the footer). At the moment the customizer displays all the 30+ widgetised areas in the site. How to make it show only these 3 widgetised areas that are on the viewed page?