A workshop was a room where items were constructed and planned.
In 2268, one of the Alice series androids assured James T. Kirk that the planet Mudd's research laboratories and workshops were "extremely well equipped." She and another Alice added that the crew of the USS Enterprise was free to visit them. Kirk replied that they might do so later. (TOS: "I, Mudd")
When Miles O'Brien planned to build an arboretum for his wife in 2371, essentially turning her botany profession into a hobby, Julian Bashir rhetorically asked him whether he would be satisfied with sitting in a workshop building nano-circuit boards and playing with tricorders instead of working as an engineer. (DS9: "The House of Quark")