Computer Configuration > Administrative Templates > Microsoft Edge - Default Settings (users can override)
Both
HKLM\Software\Policies\Microsoft\Edge\Recommended
This policy enables origin-keyed process isolation for most pages, which improves security by separating content from different origins into distinct processes. This may increase the number of processes created. Users can override this setting by using command-line flags or edge://flags to turn the feature on or off. If you enable this policy, most origins will be isolated, even from other origins within the same site. For related configuration, see the IsolateOrigins and SitePerProcess policies. If you disable this policy, origins will not be isolated from the rest of their site unless the origin explicitly requests isolation. If you don’t configure this policy, the browser will decide which origins to isolate and when. By default, this feature is disabled. The default state may change in the future.