How to modify default screenshot name in Firefox DevTools?

[TechAndNews]

Went into about:config.
Typed screen.
Changed "screenshot --fullpage" to "screenshot".
Would like to remove spaces and change the date/timestamp to:
screenshot-%Y-%m-%d-at-%H%M.%S.png
Which would create this:
screenshot-2016-12-18-at-1656.04.png

Seems to be no info on configuring default name for screenshots at Mozilla Developer Network:
https://developer.mozilla.org/en-US/docs/Tools/GCLI