Yes, you can.
Just cut the wire at the outlet side of your switch (after power it down ofcourse), mount a socket part of a extension wire at the end (which is connected with your switch) and mount a standard grounded plug part at the wire from your washing machine.
Good question, I have two separate groups.
I think its only safely possible to put the Circle before the switch and then you measure on 1 circle the 2 machines.
Depending on the usage and standby power you have a chance to determine which machine was on.
I only have one group available for the two machines but luckily they do work together (ie. at the same time). So I think i do need two circles to measure. So what's the best solution?
Do take care not to exceed the maximum total allowed power consumption for the circles. (3680 watt) a washing machine and dryer combined can exceed this (depending on how efficient they are)