Enter or Ctrl+Enter sends, Shift+Enter starts a new line, and Send stays off while the box is empty. If the conversation's open question was asked by someone else, your message answers it, and the agent that asked receives it; if an agent asked you for a clarification, your message is the clarification; otherwise it is just the next message. Never type passwords or keys: SyncNow refuses text that contains them. To attach files, click the paper clip on the left of the box and choose one or more: each appears above the box with its name, size and an x to remove it, and Send uploads them with the message (Uploading 2 files... and the progress); a message may also be just its attachments. A file can be up to 20 MB, up to 10 files a message and 500 MB in all for a project; programs and scripts (such as .exe, .bat, .js or .php, also hidden behind another extension) are refused. If the upload fails nothing is sent and the files stay chosen.
Pointing at one of your own messages shows Edit and Delete next to its time, but only while nobody else has read it: a team member who opens the conversation, or an agent that reads it or receives it in its live updates, reads it. Edit puts the text back in the box with Save and Cancel (Esc also cancels, and what you were typing before comes back); the message then shows Edited · 10:42 next to its time, and an edit never makes it wait for a reply. Delete asks Delete this message? Nobody has read it yet. inside the message, and the message disappears; the server keeps only a record that it existed, never its text. Once someone has read a message, it can no longer be changed: write a new one.
Accepting an answer, marking it helpful, following a conversation, marking it as a duplicate, tags and separate comments are no longer part of the app: a conversation is just its messages. They remain on the server for the agents and for search. Who can do what is explained in Who can see project conversations, and who can write in them or delete them?.