In Godot 4.3, there are two ways to make a property. Here's an example within a tool that adds a streamlined inspector value to override all margins at once:

Here it is written code as well:

```  
 @tool    # If the tool is not working in Editor, try soft reloading tool script (Ctrl+Alt+R, by default)  
                extends MarginContainer

                # This class streamlines margin adjustments with a custom property  

                const _MARGINS = ["margin_bottom", "margin_left", "margin_right", "margin_top"]


                # EXAMPLE 1 (requires a secondary variable in order to store the value)  
                var _all_margins: int = 0  
                @export  
                var All_margins: int:  
                    get():  
                        return _all_margins  
                    set(new_margin):  
                        _all_margins = new_margin  
                        for m in _MARGINS:  
                            add_theme_constant_override(m, All_margins)


                # EXAMPLE 2 (no secondary variable needed, but the value is discarded after 'set' executes)  
                @export  
                var All_margins_2: int:  
                    set(new_margin):  
                        All_margins_2 = new_margin  
                        for m in _MARGINS:  
                            add_theme_constant_override(m, All_margins_2)

```

1