It happens from time to time, that you have to change the type of created messages e.g. from synchronous to asynchronous and vice versa when designing software. Currently this is only possible by deleting and creating new messages, where the previous text has to be entered again.  
It would be helpful if the type could be changed directly in the options of a message.

STEPS TO REPRODUCE
1. start umbrello
2. add sequence diagram
3. add two objects
4. add a synchronous message with a long text for a custom operation
5. try to change the type of the message to asychronous

OBSERVED RESULT
There is not way to change the type of the mentioned message. You need to recreate the message.

EXPECTED RESULT
There should be a way to change the type of the mentioned message

ADDITIONAL INFORMATION
As an addition to a new entry in the sequence message options dialog, a corresponding context menu entry would be useful.