In City’s 1980’s Official Plan, the intent for Trefann Court was detailed in its own secondary plan (back then, called a Part II plan). But forty years later, almost all mention of Trefann Court’s significance as a “neighbourhood” has disappeared from city records.
It takes a lot of digging 
through search results to find any reference to Trefann Court on the city’s website; it’s buried in these PDF documents:
• Cabbagetown Southwest Heritage Conservation District Study Report, June 2019. Trefann history mentioned on page 35-36 (of Chapter 2: History and Evolution).
• King Parliament Secondary Plan Review, 2019. See page 14 for Trefann history.
• The only other significant link is to the City of Toronto Archives’ collection (see urban planning topic): author Graham Fraser’s records relating to Trefann Court
Fortunately Trefann Court’s informative Wikipedia entry is a top Google search result. And Toronto City Hall hasn’t totally forgotten us; Trefann Court appears on the city’s wayfinding signage. “The Toronto 360 (“TO360”) Wayfinding project is a pedestrian wayfinding system to help make Toronto a more walkable, welcoming and understandable place for visitors and residents alike.” Toronto committed $11.8 million to invest in the TO360 Wayfinding Project, using a variety of sign types: “wide totems” “narrow totems,” “fingerposts,” and “wall signs” (CBC, Sept 2018). See explanation of map features: landmarks, local destinations, community assets, districts.
Queen / SumachFront / SumachKing / Sumach
The “high level” Toronto Visitor Map identifies Corktown but not Trefann Court. Trefann Court residents might notice possible minor inaccuracies in local wayfinding signs: The fingerpost at the SE corner of Queen/Sumach is immediately south of Trefann’s boundaries, but doesn’t list Trefann. That fingerpost is within Corktown boundaries, but directs pedestrians to head south. Trefann is shown correctly on the fingerpost at King/Sumach, as well as map “totems” at Queen/Parliament and Cherry/Front.
Good to see that Trefann Court is identified by TO360 Wayfinding Project (although likely only older urban planning aficionados will know of the neighbourhood’s significance in Toronto’s recent history).