A workflow INPUT node’s { "target": "slack" } notification takes no other attributes and always sends a direct message to each responder. Workflows that start from a Slack thread can’t place the approval buttons in that thread, so reviewers have to switch between the thread that has the context and a separate DM that has the buttons. Adding optional channel and thread (thread_ts or thread URL) attributes, resolvable from workflow data, would keep approvals in the thread where the request lives.