is there a way to paste multiple slides from PowerPoint into Impress?
On LO 126.96.36.199 you have to convert a Powerpoint presentation into ppt Format (97-2003 Office); the import form reads MS Powerpoint 1-4 and 95’s, but the mentioned later format worked on my machine.
LO does not import pptx formatted presentations/slides. But you can open and convert the entire pptx presentation.
When you have done so you may import (“paste”) the entire ppt presentation or some single slides (import dialog offers different possibilities).
The way to import some/all slides in an existing Impress presentation is via
menu Slide | Insert File from Slide…