xara copy/pastes a selection across multiple layers back onto the same layers [layer structure] by default

you can then right-click on one of the pasted selections in the gallery and click Move to Current Layer if you want all the pasted selection on the same layer, which is ok if you are happy with the default as the norm

but if you would rather the selection across layers all went to the current layer by default there is a registry key - change the value from 1 to 0 :

Computer\HKEY_CURRENT_USER\SOFTWARE\Xara\XtremePro x64\18\Options\Clipboard\MultiLayerClipboard

[for version 18 - other versions will differ accordingly]