Give priority to a group if the Editor is already active

For #70020

We seem to use the readonly property way of exposing these values more widely. Standardizing this a bit across the codebase

openEditor can return null

More manual conversion of index based for loops to for-of loops

Replaces many loops of the form:

```js
for (let i = 0; i < elements.length; ++i) {
    const i = elements[i];
   ...
}
```

with:

```js
for (const element of elements) {
    ...
}
```

Mix of a horrible regex based find/replace and manual touch ups