Computer Configuration > Administrative Templates > Microsoft Edge
Both
HKLM\Software\Policies\Microsoft\Edge
Configures the amount of memory that a single Microsoft Edge instance can use before tabs start getting discarded to save memory. The memory used by the tab will be freed and the tab will have to be reloaded when switched to. If you enable this policy, the browser will start to discard tabs to save memory once the limitation is exceeded. However, there is no guarantee that the browser is always running under the limit. Any value under 1024 will be rounded up to 1024. If you don't set this policy, the browser will only attempt to save memory when it has detected that the amount of physical memory on its machine is low.