Sync v2: Notify users that data types need to be checked on newly added device as well

[Miyayes]

Description

Based on reports, many users (including myself) are misled into thinking that Sync v2 is not working when they connect a new device to an existing Sync chain because they do not realize that they must check the relevant data types on the newly connected device as well. The interface does not immediately indicate this upon joining a Sync chain.

Feedback from user:

Brave really needs to make those sync checkmarks more visible whenever you add a new device. Currently, whenever you add a new device, it just gets added to the sync chain without ever notifying the user that only Bookmarks are synced by default.

Possible Solution

Make the checklist interface more visible immediately after joining an existing Sync chain, or open a modal/notification.

[bsclifton]

cc: @jsecretan

[Miyayes]

+1 https://www.reddit.com/r/brave_browser/comments/iwgopp/i_synced_a_new_pc_and_nothing_is_being_synced/g607rjs?utm_source=share&utm_medium=web2x&context=3