The standard absolute value function is supported, generating ABS (expression) and returning a positive value of the same magnitude with type matching that of expression or float if expression is a character type. When dragging an Absolute Value into a variable, the following tree element is created.
Variable Creation > Input > Variables: SQL Elements pane - Arithmetic > Absolute Value
Columns and/or other expressions can be moved over the (empty) branch of the tree.
There are no special properties for the Absolute Value function.