Chat & overlays
How to combine Twitch and YouTube chat in one window
Every platform's chat in one column, so you are not reading three windows at once. It is called Multi-chat in the sidebar.
The Multi-chat page merges messages from each connected platform into a single stream, in the order they arrive. Each message is marked with the platform it came from and carries the sender's badges.
Replying
What you send goes back out to the platforms you are connected to, so you answer once rather than repeating yourself in each window.
Unified chat needs platforms connected by signing in. Destinations added by RTMP address relay video only and have no chat to read.
Subs, gifts and raids
Twitch events appear in the feed as their own kind of row, with a coloured rule down the left, so a subscription does not read like somebody talking and get scrolled past. Subs, resubs, gifted subs, gift bombs, raids and announcements are all included, using Twitch's own wording.
Events show as they happen but are not replayed after you reload the page. Messages are.
Timestamps
Tick Show how long ago each message arrived above the feed to put a "4m ago" label on every line. Your browser does the timing against its own clock, so it costs no platform quota, and hovering a message shows the exact local time.
To put chat on your stream rather than just on your screen, see Chat overlay in OBS.