I have some sysex files that I want to transfer to a synth. But as far as I can understand the only way to open the sysex editor is to record sysex INTO cubase. Is it impossible to just open the editor and load the sysexfile from my PC?
Try importing it to a MIDI track and opening the List Editor.
You can import SysEx if it’s in .SYX format.
Create a sysex event in the list editor and click on the comment box to open the sysex editor where you can see the export/import dialogs