Allocating more memory to LibreOffice fixed the performance issue for me on around one dozen Mac OS Sierra machines:
In the LibreOffice Menu go to LibreOffice > Preferences (on Windows and Linux go to Tools > Options)
In the Options dialogue window choose LibreOffice > Memory
Allocate more memory, for instance:
Use for LibreOffice: 1'024 MB Memory per object: 64.0 MB Remove from memory after: 00:30
Cash for Inserted Objects:
Number of objects: 100
Of course the amount of memory you can allocate to LibreOffice is limited by the RAM available on your box. So you might wanna find your optimal configuration by testing different memory settings.
Mac OS Sierra needs significantly more RAM than older Mac OS versions. If your box has less than 8 GB RAM available then consider upgrading to 8 GB.
Hopefully this will work for you too!