To train you tempo stability you can mute the metronome for several bars.
When activated (silent Bars > 0) the playback alternates between played and mutet bars. Use the shown wheels to set the length of these segments. The settings above would result in the following playback:
If you check the "Random" field, the amount of bars will become a random number between 1 and the value set in the wheel. In the example, the grey colored bars may be played or skipped: