The SMS editor is currently limited to a single part SMS and assumes that the message will be encoded using the GSM character set, allowing 160 characters.
As of OVPMS-1907, OpenVPMS supports multi-part SMS messages for automatic appointment and reminders.
The editor should be updated to:
support multi-part messages up to the limit of the SMS provider configuration
determine which encoding will be used, and limit the no. of characters accordingly