Hi and thanks for reaching out. My name is William. I'm a Windows technical expert. I'll be happy to help you out today.
This information is reflected in a DWORD named TextScaleFactor in HKEY_CURRENT_USER\SOFTWARE\Microsoft\Accessibility
By the way, for purposes of forum archive, the answer comes from usage of Process Monitor. There is saying amongst IT professionals: "When in doubt, Process Monitor." In this case, just set a filter for RegSetValue, make the change, examine the output for process SystemSettingsBroker.exe