Hi!
I know that there is SPC x to open the scratch buffer, but is there also a similar shortcut to quickly close/hide it again? Of course I can always CTRL x 0, but that feels clunky.
SPC x
CTRL x 0
The default keybinding for killing a buffer should be SPC b k. That is what I use to close the scratch buffer. 
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The default keybinding for killing a buffer should be SPC b k. That is what I use to close the scratch buffer.