NOTE: This issue has been fixed as of Cerberus FTP Server version 10.0.11.0.
If you want to use 'enter' to wrap to another line, there are a few solutions, depending on your version of Cerberus:
1) If you have Enterprise Edition, you can manage your message via the web admin portal. Navigate to 'Server Manager' > 'Messages'. When editing the message there, hitting enter there will wrap to another line.
2) If you have the Standard or Professional editions, you can edit the messages in Server Manager. Click 'Configure', then 'Msgs' at the top. Draft your desired message in a text editor such as Notepad, highlight all the text, and CTRL-C (or right-click > 'Copy') to copy it.
To paste it into your desired message window (e.g. Welcome Message), CTRL-V (or right-click > 'Paste'). There is a known issue that hitting 'enter' closes the Server Manager window, so do not hit 'Enter'.
3) In all editions, you may also use the legacy Server Manager. In the Cerberus GUI, go to 'Tools' > 'Server Manager (Legacy)' > 'Messages'. You may use 'Enter' to wrap lines in this management tool.