Hi,
Not sure my exact situation matters, but when loading Brave after a restart (or just random tab clicking if it’s already inactive) a tab may become activated that you want inactive, but not gone.
Being able to kill a tab from it’s right click menu would be a great shortcut compared to opening the Task Manager and finding the tab end end it that way.
Thanks in advance for considering it 
If you want to ‘freeze’ a tab, put it in a Tab Group and then collapse it, Chromium already set that system, only domains that have Notification permissions will not get the freeze state, for example, so you can selectively stop this behavior in the domains you want by manually adding them as notifications, even if they don’t use or have any notification system.
If you close a tab through task manager, that will close the tab… which you can already do by hitting the x button.
You can also manually discard tabs in brave://discards/
And also, use the memory saver feature to do the same by enabling flags to improve its behavior and set times and all that.
brave://flags/#memory-saver-multi-state-mode
brave://flags/#memory-saver-discarded-tab-treatment
brave://flags/#memory-saver-memory-usage-in-hovercards
brave://flags/#memory-saver-discard-exceptions-improvements
brave://flags/#memory-saver-savings-reporting-improvements
There is also Tab Group save as flag in Chromium brave://flags/#tab-groups-save, but it can be a little buggy, especially in Private mode, so you can use an extension to do the saving and restore of groups like Tab Groups Extension, which means you can close and restore any group you want without having to have the tabs on the browser loaded.
But Chromium tab group save, seems to be the better way in the future since it starting to get sync support and all that, and it rarely causes crashes, at least in normal windows.
There is no need for a feature request like this, which to be honest, it’s hard to understand why you even mean, because you are mixing terminate and then task manager and then say “inactive but not gone” so I think my answer is the correct one of all the methods Chromium/Brave have for this, especially with the use of Tab Groups being able to freeze tabs completely on collapse.