JSON input - Get Fields button missing from fields tab

Hi,

I'm a new bee to PDI, while working with JSON input file i observed there is no get Fields button from "fields" tab to bring JSON file metadata in step(usually i have seen most of input steps has this feature). all the time I'm doing hard coding my self in JSON input step which is annoying.

is there any work around to achieve and bring metadata into "fields" tab with out hard coding from JSON input file.