Lieutenant Gabler was a 23rd century Starfleet officer serving aboard the USS Enterprise under Captain James T. Kirk. He was one of Montgomery Scott's best engineers, who also doubled as a security officer and a helm officer.
In 2269, when Scott and Kirk carried a force field box, containing an antimatter villus from the "digestive system" of an unidentified cosmic cloud, into the nacelle of the Enterprise, Gabler assisted Scott remotely, by opening and closing the doors to an area at the rear of the nacelle where the antimatter was placed. (TAS: "One of Our Planets Is Missing")
He was in engineering when Kirk called, expecting Scotty, and ordered him to raise the deflector shields, but he couldn't as the Vendorian posing as Carter Winston had disabled them. (TAS: "The Survivor")
He and Bell, while acting as the relief guard for the dilithium vault, found two Klingons "poking around". When he brought the matter to James T. Kirk's attention, they claimed to be lost. After Spock offered to show the Klingons the way, Kirk told both officer to remain at their post until they were relieved. (TAS: "The Time Trap")
When Scott asked him why the bridge was experiencing zero gravity, he believed the problem was in the gravity control computer, but was unable to access it because the computer bay hatch was jammed. (TAS: "Once Upon a Planet")