A window shade comprising: a reel coupled to a first control module , the first control module being operable to drive the reel in rotation; a panel assembly connected with the reel and including a plurality of transversal vanes respectively connected with a first and a second panel , the panel assembly having an open state for light passage and a closed state blocking light passage, and the reel being rotatable to wind and unwind the panel assembly ; a lift actuator coupled to a second control module , the second control module being operable independently from the first control module to drive the lift actuator in rotation, the lift actuator being rotatable in a first direction to urge the first panel to slide relative to the second panel for switching the panel assembly to the open state, and in a second direction to release the first panel for switching the panel assembly to the closed state; and a switchable coupling mechanism having a coupling state and an uncoupling state; wherein the window shade has a first configuration in which the panel assembly is in the closed state and the coupling mechanism is in the uncoupling state, and a second configuration in which the panel assembly is in the open state and the coupling mechanism is in 10 the coupling state; the window shade being characterized in that the coupling mechanism is rotationally coupling the lift actuator to the first control module in the coupling state and rotationally uncoupling the lift actuator from the first control module in the uncoupling state, wherein the coupling mechanism includes a switching part that is rotationally coupled to the lift actuator and has a drive transmission portion , and a transmission assembly coupled to the first control module and including a transmission member , the drive transmission portion of the switching part being engaged with the transmission member in the coupling state and disengaged from the transmission member in the uncoupling state. a reel coupled to a first control module , the first control module being operable to drive the reel in rotation; a panel assembly connected with the reel and including a plurality of transversal vanes respectively connected with a first and a second panel , the panel assembly having an open state for light passage and a closed state blocking light passage, and the reel being rotatable to wind and unwind the panel assembly ; a lift actuator coupled to a second control module , the second control module being operable independently from the first control module to drive the lift actuator in rotation, the lift actuator being rotatable in a first direction to urge the first panel to slide relative to the second panel for switching the panel assembly to the open state, and in a second direction to release the first panel for switching the panel assembly to the closed state; and a switchable coupling mechanism having a coupling state and an uncoupling state; wherein the window shade has a first configuration in which the panel assembly is in the closed state and the coupling mechanism is in the uncoupling state, and a second configuration in which the panel assembly is in the open state and the coupling mechanism is in 10 the coupling state; the window shade being characterized in that the coupling mechanism is rotationally coupling the lift actuator to the first control module in the coupling state and rotationally uncoupling the lift actuator from the first control module in the uncoupling state, wherein the coupling mechanism includes a switching part that is rotationally coupled to the lift actuator and has a drive transmission portion , and a transmission assembly coupled to the first control module and including a transmission member , the drive transmission portion of the switching part being engaged with the transmission member in the coupling state and disengaged from the transmission member in the uncoupling state. <EOS>