Feature request #15513
Diagrams: no friendly interface to update an existing expression (too hard)
|Pull Request or Patch supplied:||No||Resolution:||fixed/implemented|
In layers's properties > Diagrams you can set an expression to build your diagram
Then if you want to rewrite this expression, double-clicking the expression simply offers you to write it within the text box, which is not easy nor friendly at all when you are using a complex expression.
I think that double-clicking an expression or at least, select the expression and push the expression builder button should open the expression builder dialog (prefilled with the current expression, as done when a field is selected in the left column) for an easy typing