Shortcut/app to capture only the content of a window in a screenshot?
I'm not sure how convenient this would be for your workflow...


Switch to fullscreen.
From the View menu, uncheck "Always show toolbar in full screen"
Use  Cmd ⌘   Shift ⇧   4  then tap the spacebar &amp; click in the window
This will [as always] take a snap of the entire window - but in this case it will leave out the toolbar entirely.
Scrollbars will hide or show depending on your setting in System Prefs > General