hi, just want to ask
How to make multiplayer game for .wdl?
For Lite-C, I have read about send_var_id and session_connect
Is there any equivalent functions or plugins for wdl?

There are third party plugins like my ANet plugin. ANet can be used with A6/A7 C-Script/Lite-C. (see signature!)

senssion_connect can only be used with gamestudio professional and send_var_id only with Lite-C.
But I would advice you to use a plugin for multiplayer and not the built in system because it lacks of confort and possibilities.