I'm not using the Transpose feature, I'm referring to a key change within a piece. The piece I was working on starts in F Major then later, part way along a line, changes key to C Major. There is no problem changing key since all subsequent lines don't have the flat sign at the start on the B line of the treble clef, as required by the key of F Major. However, the exact point at which the key changes from F Major to C Major needs to be indicated by a natural sign on the B line of the treble clef.
Hopefully this feature, whereby the exact point of a change of key from any other key to C Ma