Can I use an ELV dimmer to dim an electronic switching power supply for LEDs
Doubt it. From the datasheet/installation guide: 


  Blockquote 1. CAUTION:To avoid overheating and possible damage to other equipment,
  do not use to control receptacles, fluorescent lighting fixtures, motor-operated or transformer-supplied appliances.
  2. Use only to control the primary side of electronic transformer-supplied
  low-voltage lighting, or in combination with incandescent lamps.
  3. This product requires a neutral wire in the wallbox.
  Blockquote


At some point you may reduce voltage to the LEDs such that they dim or just go out.  I do not know if this will damage your LED strip.  I would investigate this: TLC5940 which is a PWM controller for LEDs.  It is ~ $4.20 vs. $70.00 USD and while it may require some external componenets it will be a superior and less expensive option.