You’re referencing the rotated tile name, you need the base id instead.
The following JSON worked for me.
In start_locations.json:
{
"type": "start_location",
"ident": "research_lab",
"name": "Research lab shelter",
"target": "lab_surface_brick_basementD1_hidden_lab_stairs"
},
in scenarios/scenarios.json:
{
"type": "scenario",
"ident": "evacuee",
"name": "Evacuee",
"points": 0,
"description": "You have survived the initial wave of panic, and have achieved (relative) safety in one of the many government evac shelters.",
"allowed_locs": [ "shelter", "shelter_1", "shelter_2", "research_lab" ],
"start_name": "Evac Shelter",
"flags": [ "CITY_START" ]
},
I’ll add some information about this to the guide for 1st time contributors.