I have the latest updates and guest additions installed (I can copy and paste text from the host to the VM, but I can’t drag and drop files in either direction. Obviously, Drag and drop is set to bidirectional.
When a drop is attempted from host -> VM, I get ‘link here’ (KDE version of manjaro) instead of copying something.
From the virtualbox manual it seems the file manager used may influence the behavour.
The manual also mentions the installation of the guest utilities. On Arch and therefore probably Manjaro as well - some of the functionality from the guest utilities is built into the kernel which may explain why some prebuilt VirtualBox functionality behaves differently on Manjaro installations.