Vivaldi has this feature called hibernating tabs. I believe Edge calls it sleeping. Currently, Edge has some settings to make tabs go to sleep automatically after a period of inactivity, but I would like an option to do so manually by the tab's context menu.
There are two menu options that would be very useful:
Hibernate Tab (affects only the right-clicked tab. ignores "never put to sleep" settings)
Hibernate all Background Tabs (affects all background tabs in the current window, excluding pinned tabs and the domains/urls you've specified in the settings to never put to sleep)
While there is no such option currently, you could do the reverse.
In the Address Bar go to edge://flags/#edge-sleeping-tabs-immediate-timeout and in the dropdown next to "Enable immediate timeout for sleeping tabs" set it to "Enabled", then restart Edge. Once Edge is back up, go to edge://settings/system and set the "Put inactive tabs to sleep after the specified amount of time" dropdown to the maximum time.
Essentially this would then mean only sites you're actively-using will remain active during your session. Not-quite the same as being able to right-click and choose "Make tab sleep", but hopefully a workaround for now.