I understand what you are seeking....

However, Inkscape is *not* a 3D application. 

You are seeking 3D functionality in a **non-3D** application. What you want to do is **not possible** in Inkscape, unfortunately.

What you have are flat, *non-dimensional*, objects. i.e. just 3 rectangles with sides at various angles, that's all. You can pull the rectangles apart and see that there's absolutely no 3D projections taking place. Similar to what can be created in *any* 2D vector application. This animation doesn't utilize Inkscape specifically, but to explain further....

[![enter image description here][2]][2]


The above may *look* like a 3D projection at the end, but it's not. It's still just flat 2D objects which have had angles adjusted to *appear* dimensional. 

Any apparent dimensioning is just *appearance*, not *real* dimensional projections. As far as I'm aware, Inkscape doesn't create real 3D projections, including isometric projections. You need a 3D application for that.

**If you wish to change the view angle, you must *redraw* at the angle you want.**

Inkscape, like all 2D applications, understands X and Y on flat, perpendicular planes... meaning...

[![enter image description here][1]][1]

Inkscape has *no clue* what Z is or that it even exists.

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You can see here how users can create the **appearance** of 3D in Inkscape, but they aren't creating *actual* 3D objects: https://www.educba.com/inkscape-3d/


  [1]: https://i.sstatic.net/LHeqr.png
  [2]: https://i.sstatic.net/ME9w4.gif