Nibal,

All transitions between sizes will be labeled automatically.
Any additional labels you would like to add can be done so easily as you have found. There is no ability for the system to know where you think labels should best be located for clarity of the plan.

Regarding the callouts not deleted, it may be possible that you copied a pipe label? Otherwise, if this happens in the future, you should be able to Undo the operation, and then send the file to us to investigate.

--J