Disables Discord automatically marking a channel as read, and adds a button at the bottom to do it manually
When you click a channel in Discord, Discord will mark the channel as read automatically. With this extension, that automatic request will be blocked, and instead a button will be placed at the bottom of the channel's messages. Clicking it will perform the blocked request, marking the channel as read.
Source code: https://github.com/MarkMendell/discord-manual-unread/