While hovering the Rey menu in the admin bar, you will find the Refresh menu containing multiple buttons which are meant to refresh and flush various caches made by some of Rey’s functionalities, all meant to improve performance.
This stores all of the Customizer’s controls CSS generated styles. Rarely needed though.
Assets Cache (CSS/JS)
Rey has a mechanism which loads small stylesheets and scripts that are used on demand only, merged all together. This will cleanup the cache folder basically to be renewed on the next page reload.
Some features such as the Product Grid widget has the ability to be lazy loaded, which means it gets loaded through Ajax. Because the output is served the same to all visitors, it’s wise to cache this response, and Rey does this (actually in 2 layers, server side and client side).
This button will flush the ajax cache.
When not using a caching plugin menus are quite heavy. Since they’re rendered exactly the same to all visitors, why not cache its output. Starting with Rey 2.4.5 , it’s added and enabled by default for Menu Navigation widgets (elements in Elementor). For the main header navigation though, it needs to be manually enabled in Customizer > Header > Navigation. That’s because this is a much more complex structure and needs thorough testing.