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.
Any apparent dimensioning due to the isometric angles 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...
Inkscape has no clue what Z is.
Any apparent dimensioning is done by adjusting the angels of flat objects. This animation doesn't utilize Inkscape specifically, but to explain further....
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.
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/