• VSCode Version: 1.14.2
• OS Version: Windows 10 Creators Update

This is just a suggestion.

Almost all IDEs allow us to set a 'Single Instance Only' option, When this option is true, And you try to run a task that is already running, It'll kill the running task and then restart it.

VS Code gives an error stating that the task is already running, go to F1->Terminate Task to terminate the task.
This gets really annoying on some machines where to access Function keys, You also need to hold down a separate "Fn" key.

My suggestion is to let people specify a SingleInstanceOnly option in tasks.json, If this option is true, then instead of giving an error to user, It should kill the existing task and restart it.
And if this option is false, Then just do what it does currently.
Default value should be false, So, Only the people who really need this option can set it and others will see the usual behavior

And, I'd like to work on this, if that's okay.

Regards
Ishan