Hello,
getting to know how to use Inkscape. It looks promising.
I would like to know if there is a way to put this new drawn shape into the toolbox. My aim is to avoid me to redraw an arrow each time.
So my use case would be:
1) draw an arrow (I found some tutorial on this)
2) put this arrow in the toolbox (this is actually my question, how to do this)
3) Use this newly added arrow into any new document and resize or rotate it.

Thanks a lot for your support.

There are no ways to customize toolbars yet. But you can help yourself in other ways.

Draw the arrow and group it, you might want to adjust the document size to fit the arrow.
Create severals objects like that, that you might want to use later, and save them each in a new svg file, and keep them in the same folder.

When you want to use those objects in another document use the Open dialogue as if it was a toolbar, keep that window open somewhere on your screen so when you need any of those objects you can just drag and drop them into the new document.

Thanks, that's an idea.
For the moment I will do like this.
Another idea someone?