Please see attached gif.

Tried pressing "OK" before switching tab in the game client?
Tried adding mods manually, and running the game locally?

I tried adding mods locally and it is not working, which is why I trying this method.
If I set the "Enabled Mods" to true and then press Ok before switching tabs the window closes. If I go back to the settings window the "Enabled Mods" option is set to false. You really think I did not try this before ?

Don't know, you didn't say what you had tried, only showed what you did in the .gif.

As I have said before, some mods have prerequisites, all of which needs to be compatible with your version of the game.
If either of the requirements are not updated for your version of the game, the mod won't work.

You also don't say what mod you are trying to use, or what game version you are trying to mod.