Hello everyone.
Following the Help: 

Tools > Equations, Equation View, 
In the Global Variable section, i can see grey 'Add global variable' which disappears when I type:

Drod

Pressing Tab key:

It becomes "Drod" and sign = appears in the Value/Equations column

Typing: 1.5 

Units: mm from the drop-down sub-menu

Green appears in the cell, indicating that the syntax is valid.

But the global variable value does not appear in the Evaluates to cell. The cell remains grey and non-editable and the cursor does not move to the next cell in the Comments column. The Comments is white, but non-editable.

IF TO PRESS OK: 'There is a syntax error in the active Equation. Do you want to exit the dialog box?

                            IF TO PRESS Yes: The box disappears but when re-opening it, the  Global Variable section is empty.

IF TO PRESS "Rebild" icon: Global Variable section becomes empty.

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Also in the sketch, Dimension > DoubleClick > Modify dialog box, I cannot obtain the Global Variable icon (blue globe with yellow star), which I managed to obtain once in the past with this software.

Maybe the Global Variable functionality is somehow turned-off in this software?

Maybe the software is damaged by Users?

Any idea how to recover it, please? 

Thank you.
(A beginner in SolidWorks)