When clicking “Sync vault now” (Settings → Vault options), there is no visual feedback indicating that syncing has started. It makes the user doubt whether the interaction (clicking the button) has actually happened, and causes friction.
The only current indicator that the request to sync has been received happens after sync completes, in the form of a toast (popup). This is good, but it is not enough.
A simple spinner animation (such as the one shown upon opening the extension) would help a lot.
Jumping in here, for me, the sync usually completes in just a second or two, but I still find the lack of immediate visual feedback a bit confusing. Even with a fast sync, it’s not always clear if the click registered, especially if there’s no spinner or loading indicator. Some sort of quick visual cue would definitely improve the experience.