[Selection] Feature parity between selection and (vector) shape tools

[Intuos5]

Observation
In Affinity Designer there are multiple input options using the modifier key for shapes, these include:

1. Holding shift to constrain to proportions (square, circle)
2. Holding ctrl to scale the shape from the centre out
3. Hold alt to ignore snapping
4. Hold spacebar to move the shape (this is not in the tool description at the bottom of the window though).

Expectation
However, in Designer, I may expect this to work for selection tools as well, whereas it currently does not. As you can see from the video, while using the same sequence of actions, there are things I expect to be able to do from using the shapes tool, that I cannot replicate with selection tools.

Proposal
My proposal for how it ought to behave is listed in italics below the observation of actual behaviour.

1. Shift does constrain proportions (square, circle)
   This decision means you cannot use shift to add to a selection. In Photoshop, holding shift allows you to do both, first you hold shift to add to a selection (mitigating the need to reach to the toolbar for this) and after the initial click, you can release or press shift again to constrain the shape if needed.
2. Ctrl does not scale from the centre > it moves the selection with ctrl + LMB
   However, upon the initial creation of the selection window, with the selection drawn out, I don't see a reason why holding ctrl afterwards would not constrain the selection to be created from the centre.
3. Alt does not ignore snapping > it subtracts from the selection (which is perfectly fine the way it is)
4. Spacebar does not move the selection that is currently created
   This should be added to make more refined selections possible and to ensure continuity between the tools.