Hi! I wrote a guide on page 5, but I write a polished version here.
1. Download the last Win7 compatible driver from Intel for HD Graphics. It is the version win64_15.45.19.4678
2. Download a newer version which is win10 only but contains the driver for your processor. In my case, Intel Core i7 8550U with DEV_5917. I downloaded the latest driver.
3. Make copies/backup of both folders and save elsewhere before starting editing.
4. Unzip both. From the unzipped ones, go to the new driver folder, then Graphics, then copy all components and paste in the Graphics folder of the old (15.45.19.4678) version. Note; So far in my case I didn't play a role if I replaced the same names of the old files with the new ones or skipped them to keep the old ones. Exception; do NOT replace the igdlh64.inf file and the igdumdim32.dll
5. Find the DEV number of the processor. Device Manager (from Control panel or search), right click on generic VGA Adapter, properties, details, ID (from the list).
6. Open the igdlh64 file (with a notepad) from the new version (Graphics folder) find the DEV number under windows 10 and copy the whole line.
7. Paste it under the Windows 7 section in the igdlh64 file of the old driver and correct the ikbl win10 with iskl win7 (known trick for 7th gen).
8. Copy all lines that include the 4-digit number from the igdlh64 file from the new driver and paste in the respective sections of the igdlh64 of old driver. In the end of the text, also add the name of the driver as a label, eg Intel UHD Graphics 620.
9. Install the modified old driver (win64_15.45.19.4678) and reboot.
10. After reboot. Copy the igdumdim32.dll file from the Graphics folder of the new version and paste it to the C:\Windows\SysWOW64 replace the existing files