, 
you will find in the toolbar category < Tempo>.Inserting "Ritardando" And "Accelerando"
The corresponding buttons , you will find in the toolbar category < Tempo>.
Mark one blocks over the area, over which the Tempo-change should take place.
Attention: if no block was selected, the Tempo-alteration goes until the bar-end only!
In order to set the speed of the Tempo-change, please double click on the symbol "rit" or "accel".
The Tempo marks are symbols and are therefore deleted also like symbols.
During the MIDI-Playback all ritardandos and accelerandos are taken into account!