Defaults Slack's 'also send to channel' thread option to checked
If you prefer to (or need to) have Slack threads echoed to the channel, then you know how annoying it is to have to remember to check the "also send to channel" checkbox all the time. (Or forget to, then delete the message, then rewrite it.) This extension simply checks that box for you by default.
TIP: Hide the ugly and useless toolbar item in Chrome by right-clicking on it and choosing "Hide in menu".