4-position touch dimmer - waveforms unexpected, but functional. need suggestions for soft switching
This circuit  is triggered by sensing high impedance line frequency  E-field levels on an extended wire with a finger touch. It probably (selects different delayed triggers for ) triac phases on the primary side of a transformer, quickly, after some detection delay. 

There is no provision in the design for soft switching for slew rate phase control.

Conclusion : not possible with this unit.

When I prefer soft dimming , I use a manual dimmer triac unit and defeat the instant on/off switch mechanically with a spacer. Although that takes "so much more effort than a remote control" so grandkids tend to leave it on.   There are Zigbee remote controls for LED luminaires , from Taiwan, that look pretty good as I recall.