Action bar addon that store ability positions on server?
 

Is there one or only default bars can save it content on the server? Also can I disable this cloud synchronization for default bars?

I'm not sure what you are asking exactly but Blizzard has a lot of functionality outside of our control. If something has to be stored on their servers we won't be able to stop that.

By Ability Positions. If you mean which action is on which bar slot then Blizzard handles that for their action IDs 1 to 120 ( I think ) . As long as any addons utilise those slots for their action bars then Blizzard will keep track of them (as far as I am aware). Any custom created buttons with a different action bar ID ( or no action bar ID ) then you will likely have to store the position in the players saved variable table like any other addons data you want to keep. You load it on start up and save it on shut down ( or the nearest events to those times ).

If this isn't what you mean maybe you can give an example of what you are thinking about.

I think they are talking about the synchronizeConfig/synchronizeSettings CVars.

Along with synchronizeBindings, synchronizeMacros and synchronizeChatFrames you don't get to choose which "bits" of those groups are saved to the servers.

I think the primary intent of these was for competition using the default UI so you could turn up to a computer that's not yours and have your default UI settings without needing to "plug something in"... I think. Not intended as an addon backup mechanism.