costs – Windows 7
Drag’n’Drop – bidirectional function
Common clipboard – bidirectional
But the overall buffer does not work, tell me how to fix

Answer 1, Authority 100%

As far as I remember, in V.B. Indeed there is a problem with buffer.

Unfortunately, you do not write which OS is real, but what is the virtual. Well, version V.B. would not be too much.

In my case there was a virtual machine with Ubuntu-18 Linux on a real machine with WIN-10, with the last (6.14) v.B.

I managed to solve it as follows:

1) Check that in the settings of virtuals is the desired check mark. Drag-end-drop did not activate it, it seems to me unnecessary luxury.

2) followed instructions
on the VadtBox Forum
(The problem, as it turned out, known)

In the general case, the problem in the drivers that must be put on the virtual.

In my case, it is solved by the following actions in a virtual machine with Linux:

apt-get remove -y virtualbox-guest-x11
APT-GET REMOVE -Y VirtualBox-Guest-DKMS
APT-GET REMOVE -Y VIRTUALBOX-Guest-Utils
reboot
Wget https://download.virtualbox.org/virtualBox/6.1.2/vBoxGuestAstadditions_6.1.2.iso
MKDIR / Media / ISO
Mount VboxGuestAstAdditions_6.1.2.iso / Media / Iso -o Loop /media/So /VBoxLinuxAdditions.Run
Yes
reboot