Speaking of Transform Each new absolute mode, presented in one of Beta builds (removed for now).
While having it is great (especially in the finished state), Transform still relies on one of 9 reference points.
To set a custom transformation pivot/origin we need to use interactive tools... and they don’t offer absolute lengths.

Here, take a look, a real example.

I need to scale this > shape to be exactly 20mm height — and I need it to be scaled exactly from the position I marked with guides — the bottom right corner of it.

Transform panel can’t offer me anything but three fixed positions. Sure, I can use one and move the artwork, using Snap to Grid. But sometimes it's just a very procedure — a selection is more complex than a single path, accidentally deselecting is quite easy, and reselecting with Undo is untrustworthy.

So I grab Scale tool, hold Opt/Alt and click the point.
In an ideal world I’d be able to toggle absolute mode and set 20 mm for my desired height...
In the world we are in I paste the current height (I copied in a previous step), type 20 (the desired height), multiply in instantly by 100 by adding two more zeroes (since inputs don’t support more than one arithmetic operation) and divide it by the current height value I copied beforehand (which is not always the case).

This gives me the result I wanted... but it could have been faster with the absolute mode, don’t you think?