Timeline playback: Slowmotion and fast playing with J/L
Add the key "shift" to J/L for slowmotion playback.
Holding shift and hit J/L ones which only forward 1 frame.
Still holding shift and hit J/L again sends continuously more arrow right keys. After 10 steps it plays normal speed.
After 10 steps it will play faster then normal in a logarithmic way still hold shift and hit J/L.