The Starfleet Corps of Engineers Command Liaison was the Federation Starfleet officer in charge of the Starfleet Corps of Engineers; the Command Liaison coordinated SCE activity with Starfleet Command, issued mission assignments to the numerous SCE detachments throughout Starfleet, and ensured those teams got adequate personnel and logistical support. (SCE eBooks: The Belly of the Beast, Foundations, Book Three)
The position was created in 2280, following the increased profile the Corps driven by Commander Mahmud al-Khaled. Al-Khaled was thus appointed as the first officer to the position. (SCE eBook: Foundations, Book Three)
As of 2371, the post was held by Admiral John Harriman. That year, he attempted to persuade Captain Montgomery Scott to take the post following his impending retirement (TOS - Strange New Worlds VII short story: "Full Circle") By 2375, Scott did indeed take over for Harriman, but he found the job not to his liking, and often delegated his duties to his assistant, Commander Leland T. Lynch. In August 2375, Scott went on inactive duty, though continued to serve in an advisory capacity, while Lynch took over on an interim basis. (SCE eBook: The Future Begins)
In March 2376, Lynch tendered his resignation, and Admiral William Ross persuaded Scott to return to the post full-time that April. (SCE eBooks: The Belly of the Beast, The Future Begins) Scott continued in the post into 2381. (ST novel: A Singular Destiny)
In the late 24th century, the office of the Command Liaison was located in the Tucker Memorial Building, which also served as the SCE's headquarters on Earth. (SCE eBook: The Future Begins)