JSON extension isn't known by PSPad.
PSpad opens from project known extension and unknown extensions are send to
assigned application. So I don't know how did you assign PSpad to JSON.
Open menu settings / JavaScript
On the second tab is list of assigned extensions, add there *.json

>From this moment PSpad will know JSON extension. Clicking on your manifest will
open it as any other known file directly in PSpad

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Odpovedet emailem