No longer needed, as "unload tab" is now built into Firefox, but 5 stars for the years of usefulness and inspiring Firefox to build in this functionality.

Well, it didn't work when I tested it just now, but I think it must have probably worked before? When I first started using it.
Today, a new-features list appeared in my browser after opening. Including:
"Right-click on one or multiple tabs and choose Unload Tab to help Firefox stay fast."
I am glad this is becoming a stock feature. o7 Thanks for the help in the meantime :) Godspeed

Thank you so much Frederik.

Simple and reliable. Fully under your control - unlike Auto Tab Discard, which messes Firefox up if you have too many tabs.

Users: Suggest using an optional feature to indicate which tab has been discarded:

1. Firefox toolbar "hamburger menu" (a button with three horizontal lines near the top right) > Add-ons and themes, or Firefox top horizontal menu > Tools > Add-ons and themes.

2. Locate "Discard Tab"

3. tab Preferences > check: Prepend snowflake to discarded tabs.

非常好用，但只能休眠当前标签，要是能支持休眠当前标签组就好了。

>>> PLEASE ADD TOOLBAR BUTTON AS WELL AS RIGHT-CLICK! :P <<<

Exactly what I'm looking for!

The addon requires you to have a certain version because mozilla instead of waiting to have their web extension things figured out completly before implementing they decided to release it without finishing so as new versions release they add new stuff that addons can do and unloading tabs is only able to be done on that version fordward.