In Adobe Photoshop, if you are working with an embedded smart object that does not fit the canvas and you want to access scaling manipulation options, you can use the following keyboard shortcut:
Ctrl + T (Windows) or Cmd + T (Mac)
This will activate the Free Transform feature, allowing you to scale, rotate, and manipulate the smart object. If you hold the Shift key while dragging a corner handle, it will constrain the proportions while scaling.
If you want to fit the smart object to the canvas, you can also right-click on the transform box and select "Fit to Canvas" or use Ctrl + 0 (Windows) or Cmd + 0 (Mac) to fit the view of the canvas, but that does not resize the object itself.