Unable to use `preLaunchTask`

It seems there is some kind of issue/bug with the `preLaunchTask` option...
I'm unable to figure out how to make use of this.
I tried:
1. **single string value** = "Live Debug"
Pointing to a task group that looks like:
```json
{
"label": "Live Debug"
,"group": {
"kind": "test"
,"isDefault": true
}
,"dependsOn":[
"Local Live-Server (Python3)" <-- http.server
,"Watch (Rollup)" <-- Build javascript app used inside html page.
,"RemoteDebug" <-- Opens 2 new tabs, one with web and one with file URI's.
]
}
```
But it never attaches because the sub-tasks never exit obviously as intended.
The group works perfectly fine when run as task.
(The `RemoteDebug` task could be left out ofcourse)
1. **object value** =
```json
,"preLaunchTask":{
"task": "Live Debug",
"type": "process"
}
```
Gives the **error** Could not find the specified task..