The command Replace with content causes the currently set value for a variable (see under Formula [Equation] or Table ) to be permanently adopted.

That means, that the respective variable is not used in the part anymore.

When clicking on , a confirmation prompt is displayed.

Confirmation prompt if the variable shall really be removed from the entire part.

If you confirm with OK, the deactivated variable is marked in the list with a superscript star symbol (this is the usual marking for unused variables)

Variable highlighted with star icon

You can also see in the sketch history [Sketch history] that the variable has been replaced by the fixed value.