This version should work with all the previous versions + 1.20.5, 1.20.6 and 1.21, both on Spigot and on Paper.

Added MC 1.20 support.

Also added support for Lingering Potions.

Should now work on 1.19 as well.

Added 1.18.2 support

Now compatible with 1.18.
Should still work for all the lower versions as well.

Added 1.17 support.

Should still work on all previous versions.

You'll not be able to grab a full stack with middle click, but at least nothing should disappear.

I might get around to adding full support (i.e middle click for full stack) later on. Sorry for the inconvenience.

Added support for 1.8 using reflection.
The plugin will most likely work with all the versions between 1.8 and 1.13.2 but I've not tested it explicitly.