In, yes, OLDER versions of Sketchbook - when I copied a selection and pasted - it was applied to the layer I was working on. NOW a new layer is created (which is -TO ME- less than helpful).
(If I want a new layer I will simply DUPLICATE the current layer - and manipulate it)
So I suggest within >edit >preferences > general> options
that right under
"Add Image: Import into a new layer"
is
"Paste: Import into a new layer"
Or a new subheading - perhaps - "LAYERS" - so that USERS can set their preference for HOW or IF a new layer is created. Default setting to NEVER or ALWAYS create a new layer when pasting. Or create new layer WHEN SELECTION is > minimum size -
Or as HOTKEYS for copy (Ctrl+C) and copy merged (Ctrl+Shift+C) are distinguished from each other - then perhaps a HOTKEY would suffice - paste (Ctrl+V) and Paste-NEW LAYER (Ctrl+Shift+V).
Any of these would suffice. And all should probably be future options regardless of which is developed/coded first.