After discovering and getting really excited about the VR Editor mode, I was disappointed to find that it disappeared somewhere on the way to 5.3 (outside of the Virtual Production Template). After hitting a brick wall with the official documentation and finding no solution online, I decided to snoop in the default Virtual Production project files to see if I could find the magic switch to enable the mode in an existing VR template project (or any other project).
Are you able to model and texture? Have you tried it in 5.4?