Hello!

I want to give player certain effect for a certain time when he right-clicks on an certain item (for example, diamond sword). How can this be done?

The effect should remain even if it does not hold the item.

I don't think this can be done at the moment.
(Unless you use third-party scripting.)

@RomaGreat55 I just reread this issue and noticed that you are talking about 'diamond sword' (a vanilla minecraft item) rather than a custom item. Adding effects to vanilla items is out of scope for this plug-in, but adding effects to custom items is expected to be possible in the next major version.

This issue will be solved implicitly (at least for custom items) when I finish #41 .