In Sitecore, I built two custom multi-lists, where the second one depends on the first. The only issue is, that after selecting the first one, I have to save the item before the second multi-list filters the items.
My question somebody know how to create a two custom multi-list on Sitecore, where the second one filters automatically after selecting an item in the first (without save event), or which event can I override to do it?
It sounds like what you are looking for is some kind of front end event that you can use in the Sitecore backend to update a list based on another list selection without a save event. I don't think there is really anything out of the box for that..
Really what you should be doing (to do the 'sitecore' thing) would be to have your first selection (be it multi-list or whatever you like) simply point to a datasource item for another template item which is where your user can set the second option(s). I think you would benefit from taking a different approach like this rather than trying to customise Sitecore here.