Purpose of the chain link in the "Direction" setting in transform tools?

[Ofnuts]

Since 2.10.10 (according to the doc), there is a chain link between the direction setting of the transform tools:

What is the purpose? The doc says:

With GIMP-2.10.10, you can link these two options in Rotate, Scale, Perspective, Unified transform and Handle transform tools. This allows moving handles without affecting the transformation, letting you manually readjust their position.

And indeed, moving the handles doesn’t affect the transformation, but then why would we want to move then otherwise?

So how is this really used? What is the use case?

[barefootliam (Liam Quin)]

Two reasons i’ve wanted to do this - to align the handles and/or guides with things in the image (for corrective transforms), and to cope with the case that the image is larger than my monitor, and i can’t see the handles because they’re offscreen at the zoom level i need to use.

[Ofnuts]

to align the handles and/or guides with things in the image (for corrective transforms)

That always been possible, even before this was added?

to cope with the case that the image is larger than my monitor, and i can’t see the handles because they’re offscreen at the zoom level i need to use.

You can always pan, and the chain link doesn’t put them into view?

[barefootliam (Liam Quin)]

I admit i was speculating. But, panning with the unified transform tool doesn’t let you do a rotate (which must be outside the corners) and see what you want to rotate, e.g. if i’m connecting a 30,000 pixel wide scanned image, unified transform is useless. The rotate tool works, though, with a preview of grid lines, so i’m not certain where the use case for this well-buried feature came from!