Problem solved! The correct syntax is
/bind key_here toggleconsole, though my key was still not detected. I used \ which has ASCII code 92, instead in the Config.conf I got this:
<keybinds>
<toggleconsole>220</toggleconsole>
</keybinds>
So I modified that 220 into 92 and voila, as simple as that.
Note: I'm sure that LU has that problem because even though the grave accent is the normal key to open console in every game, no matter what's your layout, it will still detect that key even though if it's a ~, or a \ in my case. Also for those who have ~ the console will still open.
Thank you SugarD as by googling after your advice, you unvoluntarily made me find a solution
P.S. For those who want to know more in case their having the same issue, here is what helped me sorting this out:
[...] it can be opened and closed by pressing the button above Tab ?, known as the "tilde." ~
Note: This should work regardless of your keyboard layout. If it doesn't, [...] type bind your_key toggleconsole (replace your_key with the key to open the console).
From this link:
https://developer.valvesoftware.com/wiki/Developer_ConsoleTopic might as well be locked for me, up to moderators opinion.