Hi, Lexxko. I'm just one of the users here (not support), but if I understand right, you are saying that copy/paste works in KVM mode (as opposed to Seamless mode), but drag and drop doesn't.
Drag and drop (unless I am mistaken) is only available in KVM mode (controlling several computers on ONE monitor)... not seamless (having multiple monitors, and having a computer on each screen, and being able to move your mouse pointer seamlessly off one and onto another). Luckily, copy and paste do work.
Don't confuse the KVM mode with the KVM version of the software. The KM version only does Seamless mode. The KVM version can do both Seamless and KVM mode. And, only Seamless mode allows drag and drop.
I hope I got that right, and that it helps.