Showing angular.json and launch.json to configure Nestjs for debugging. Just use nx serve api, then launch the debugger in VS Code to attach to the Nestjs process

angular.json

{
	"version": 1,
	"projects": {
		"api": {
			"root": "apps/api",
			"sourceRoot": "apps/api/src",
			"projectType": "application",
			"architect": {
				"build": {
					"builder": "@nrwl/node:build",
					"outputs": ["{options.outputPath}"],
					"options": {
						"outputPath": "dist/apps/api",
						"main": "apps/api/src/main.ts",
						"tsConfig": "apps/api/tsconfig.app.json",
						"assets": ["apps/api/src/assets"]
					},
					"configurations": {
						"production": {
							"optimization": true,
							"extractLicenses": true,
							"inspect": false,
							"fileReplacements": [
								{
									"replace": "apps/api/src/environments/environment.ts",
									"with": "apps/api/src/environments/environment.prod.ts"
								}
							]
						}
					}
				},
				"serve": {
					"builder": "@nrwl/node:execute",
					"options": {
						"buildTarget": "api:build",
						"port": 9229
					}
				},
				"lint": {
					"builder": "@nrwl/linter:eslint",
					"options": {
						"lintFilePatterns": ["apps/api/**/*.ts"]
					}
				},
				"test": {
					"builder": "@nrwl/jest:jest",
					"outputs": ["coverage/apps/api"],
					"options": {
						"jestConfig": "apps/api/jest.config.js",
						"passWithNoTests": true
					}
				}
			}
		},
...
}}

launch.json

{
	// Use IntelliSense to learn about possible attributes.
	// Hover to view descriptions of existing attributes.
	// For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
	"version": "0.2.0",
	"configurations": [
		{
			"type": "chrome",
			"request": "launch",
			"name": "Launch Chrome against localhost",
			"url": "http://localhost:4200",
			"webRoot": "${workspaceFolder}"
		},
		{
			"type": "node",
			"request": "attach",
			"name": "Attach to NestJS API",
			"port": 9229,
			"restart": true,
			"stopOnEntry": false,
			"protocol": "inspector"
		}
	]
}