SALOME NoteBook allows to predefine numerical and boolean parameters (variables).
By default, the NoteBook is located in a tabbed widget to the left (shared with the Object Browser).
To hide/show this tab choose View > Windows > Notebook.
Here you can add new variables, remove and rename existing variables and change their values.
If you have modified some variables, which are already used in the current study, you should click Update Study button to apply your changes to the study.
Here is an example of setting variables in python scripts:
Later these values can be used as parameters for any operations in various components.