Hello,
it's normal that at rcon.io server console, Tool tab, Give Item to Player is missing of a lot of objects? For example, all electric objects. How to give something electric to players? Thanks.

That'd be a question for the developer of the tool you are using.

Isn't "rcon.io" an official tool?

Ah, missing the rcon.io reference. That's a tool provided by Facepunch I believe, but likely is manually updated each update to include that. https://github.com/Facepunch/webrcon/tree/gh-pages

You can use the Rcon or in-game console to give anything to anyone:

giveto <playername> <itemname> [number]

All the item names for electrics and everything else are listed here:

https://www.corrosionhour.com/rust-item-list/

Put 'elec' in the search box and it'll filter all the electric stuff.