Computer Configuration > Administrative Templates > Microsoft Edge
Both
HKLM\Software\Policies\Microsoft\Edge
OBSOLETE: This policy is obsolete and doesn't work after Microsoft Edge 86. This policy doesn't work, use 'SleepingTabsEnabled' (Configure sleeping tabs) instead. Controls whether Microsoft Edge can freeze tabs that are in the background for at least 5 minutes. Tab freezing reduces CPU, battery, and memory usage. Microsoft Edge uses heuristics to avoid freezing tabs that do useful work in the background, such as display notifications, play sound, and stream video. If you enable or don't configure this policy, tabs that have been in the background for at least 5 minutes might be frozen. If you disable this policy, no tabs will be frozen.