Here's what Cioks have to say about the 8800 Parallel Adapter Flex:
By using two isolated outlets the Parallel adapter Flex gives you the sum of max. currents of the two isolated outlets used. This adapter cable should be used in combination with any of CIOKS standard Flex cables if you need to power pedals with higher current needs. It gives you not only the higher current but also the possibility to choose the type of plug at the pedal end plus the cable length you need. The plug type and length is determined by the standard Flex cable used with the adapter Flex.
Please note that the Parallel adapter Flex makes a parallel connection of the two outlets used. These two outlets must be isolated from each other and MUST have the same voltage and preferably the same current rating. You get the sum of max. current ratings and the same voltage as the two outlets used. If you use it with two 9V outlets with 100mA rating each you’ll still get 9V but the double max. current which in this case is 200mA. If you use it with two 9V outlets with 200mA each you’ll get 9V and max. 400mA. Two 400mA outlets give you a max. total of 800mA.