One of my light source 5W output voltage 16-223v current 280ma customers say the slide dimmer, I have never heard of this dimmer.
For convenience, the output of 20V, 250mA (exactly 5W), 220 input, voltage drop 220-20 = 200V, 250mA = 0.25 A, then this resistor will withstand 50W power consumption at work. 50W, which is the equivalent of a medium soldering iron in it, so that the light is still working?
If there is a flash memory, it should be a thyristor dimmer. We can estimate it, and we can determine whether it's a slider resistance.
If you really use a 50W slider resistance, the cost is probably much higher than the electronic component. What's more, the 50W slider is so bulky that it doesn't fit into the dimmer.
