In the XD01 sceen (SAP ECC5.0) there exist two fields with the name "Sales organization". Normally GuiXT then uses the notation F[Sales organization.2] to denote the second field. Here this is not the case, there being two screen elements F[Sales organization]. Why? Is this an error?

The two field labels in your XD01 example are different with regard to uppercase/lowercase:

F[Sales Organization]
F[Sales organization]

In this case, GuiXT does not use the .2 notation. It is possible to address the fields separately, i.e.

del F[Sales Organization]
will delete F[Sales Organization]

and

F[Sales organization]
will delete F[Sales organization].

GuiXT always first looks for a  field where the given name matches exactly. If no such field is found, a certain set of rules are applied to find an appropriate field. The rules are:

- ignore uppercase/lowercase

- ignore space characters

- allow ending '.' for abbreviation

Therefore, given these rules,

del F[salesorganization]

del F[Sales    organization]

del F[ Salesorg.]

will all work and will delete the F[Sales Organization] field, the first one of the screen elements that matches.