Has anyone tried disconnecting / connecting a TOPsw device to the power line w. transistor or FET switch? To reduce power to 0 when TOPsw is not running, I wish to disconnect the TOPsw drain from the rectified  AC line (or disconnect its 'S' pin, X pin etc., from the low side).

Using the low side to switch the device on / off is likely easier than using the high side, but the device may not like this too much!

Using the X-pin to enable the device does not eliminate power draw from the line (from the drain pin).