It's easy to stretch an object/path horizontally or vertically using the black handles. But after it has been rotated, it is too late to make changes, except if it is a rectangle object.

Does anyone know if there is a way to do it easily? Maybe in the node editor? Workaround is to rotate it back, make the stretch and rotate it up again.

Does anyone else need this? Or it is just me?

Try this:
draw a guide along the direction of the future stretching (let's say you're stretching a path from top left to the bottom right)

activate snap to guides for the type of node that is the rightmost one

activate node tool

select all nodes

drag with ALT+LMB pressed the rightmost node along the guide.
Could this help?

Thanks @zerocinquanta

But that didnt stretch the nodes proportionally in the same way for me. With the dragged point moving more than others at the same edge of the box. Tipping the left edge as shown.

True, it's the nearest solution, but not the perfect one. I think your workaround is the only solution that gives the exact movements you require.

I seem to need it a lot. So I put in a request. https://gitlab.com/inkscape/inbox/-/issues/4661

This is how easy and natural it could be. If the stretch is in the direction of the  cursor movement.

Well done.

The Bend LPE might be what you're looking for.  Better late than never. 

@Paddy_CAD Thanks. But I'm really aiming to get the basic stretching in Inkscape improved so that it's easy for everyone to find and natural to use. And frees Inkscape from the crazy limitation of just vertical and horizontal stretching. The slogan is Draw Freely after all.  

LPEs are great if you want to keep the link to the original shape. They have a purpose, but should not be used to add functionality missing from direct manipulation. The use cases I'm looking at here are the spontaneous, instinctive way of working. Where the history is of no importance.  
I created a Gitlab issue, where there is some discussion. 

That is great. I would love to see this in future releases, ian. 

I have been struggling with this issue for years now. 

Although you can't stretch in an arbitrary direction, there's a little-known feature of the node tool that can often be used to similar effect, depending on what exactly you want to do.

If you hold Ctrl-Alt whilst dragging a node, it will tend to stick to the direction of the path. So in the case of your car image above you could do this:

• Switch to the node tool.
• Select the nodes that make-up the front section of the car.
• Hold Ctrl-Alt whilst dragging one of the nodes that forms the 'base' of the car's shape.