Declaration: TParticles.QuantityName[QIx: integer]: string;
The array property QuantityName allows to set the name of a particular quantity which is specified by the parameter QIx (valid range: 1..NQuantities). If you assign a name to a non-existent Quantity (i.e. if the QIx is less than 1 or greater than NQuantities) the call will be ignored on write or will return an empty string on read.

Hint: In order to access the particles currently loaded in the particle editor you can use the pre-declared global variable PEData.