After saving the EDID setting to the VC080, the PC’s
resolution returns to 1024 x 768 with no

display connected to the output.

How can I keep the EDID setting if I don't have display
connected?

The V080 detects the presence or absence of a display device by a signal
[+5VDc] or non-signal

on the HPD pins.

Installing a jumper between pins 18 and 19 on the HDMI side as
shown in the below figure, which keeps the EDID setting as the VC080 thinks there
is a display device attached .

The solution for VC060 is a jumper between pins14 and 16 pin
on DVI side.

The solution on VC010 is to connect three 75Ω resistors to
the following pin pairs. 

Pins 1 and 6. 

Pins 2 and 7

Pins 3 and 8.