FASTSEL is a command that has been added to GstarCAD 2022 to improve efficiency of object selection.
The FASTSEL (Fast Selection) command can be used to create a selection set of an existing object and all the objects it touches, including line, polyline, circle, arc, attribute definition, text, Mtext, ellipse and image, etc.
The behavior of FASTSEL command can be controlled by variable FSMODE.
When FSMODE is OFF (default), the selection set is the selected object and all the objects it touch.
When FSMODE is ON, the selection set is the selected object, all the objects it touch, PLUS everything those objects touch too.
FASTSEL can not only be used at the Command prompt, but also transparently in many commands at the Select Objects prompt.
See how to run the transparent command within another command by visiting the following post,