My experience is from ~2 years ago so things may have changed a bit.
Essentially there is a default view which contains all messages as usual. Each message also has a symbol next to it. If it's grey message bubble, it's a message that is not tied to any thread (it can be replied to to start a new thread. Previously if no other messages have appeared on channel so far, it can be dragged & dropped to another thread). If it's colored message bubble, it's the first message in the thread. A colored arrow means it's part of the thread with that color.
This allows you to mostly just stay in default view with all of the channel's messages. As long as people are putting the messages in the thread itself, you could quickly use the colors to see which thread the message is on (color collisions did happen, but they were fairly rare). You would need to open the thread only if you needed more context or wanted to reply to it, though replying can also be done by writing to channel & dragging the message to thread.
Essentially there is a default view which contains all messages as usual. Each message also has a symbol next to it. If it's grey message bubble, it's a message that is not tied to any thread (it can be replied to to start a new thread. Previously if no other messages have appeared on channel so far, it can be dragged & dropped to another thread). If it's colored message bubble, it's the first message in the thread. A colored arrow means it's part of the thread with that color.
This allows you to mostly just stay in default view with all of the channel's messages. As long as people are putting the messages in the thread itself, you could quickly use the colors to see which thread the message is on (color collisions did happen, but they were fairly rare). You would need to open the thread only if you needed more context or wanted to reply to it, though replying can also be done by writing to channel & dragging the message to thread.