Looks like you accidentally capitalized the L. It's FlxG, not FLxG.

Is there any output in the Cebug Console tab of the panel? From that "executing task" output, it sounds like you're on the Terminal tab.

It sounds like you might not actually be starting the debugger, but running a task instead?

Have you read the "Flash Debugging" section of http://haxeflixel.com/documentation/visual-studio-code/?

Or do I just have to set the variable's value in the new() function?

Yes.

Hm, the Flash player shouldn't just close / crash when there's an error... The debug player normally always displays a popup box with a stacktrace.

Have you tried HTML5 / is there anything in the dev console of the browser?

FlxTilemap doesn't really have a built-in way to do that, but one of the accepted graphic types is a BitmapData. You could always programatically combine multiple images into a single BitmapData with the entire grid, using copyPixels() or similar.

Another accepted FlxTilemapGraphicAsset type is FlxFramesCollection. You could probably use FlxTileFrames.combineTileSets(), which pretty much handles that BitmapData combination logic for you.

In both cases you need the BitmapData for the individual images, which you can get with openfl.Assets.getBitmapData(path).

The tiles in the tile set are graphic indexed starting with 0 (like an array). That's why it "fills the 1s with the second tile", essentially your graphic is missing tile 0 and it's all off by one. And it would crash when trying to draw tiles with index 2, because no such tile exists in the graphic.

You could just add a transparent 8x8 square as tile #0 (depending on what you want the "path" to look like).

The folder containing the neko binary, as well as std.ndll (and other .ndll files). On Windows, that's a separate directory next to the Haxe directory (C:\HaxeToolkit\neko vs C:\HaxeToolkit\haxe), not sure what the directory structure would look like on a Mac.

Is NEKOPATH set correctly? Seems relevant to that error message, according to what I linked earlier:

NEKOPATH - path to the neko installation. I believe it's needed for loading standard .ndll files.

Hm... flixel-tools calls haxelib, and it sounds like something is wrong with running the latter. What happens when you run haxelib list / haxelib path flixel?

I don't think HAXE_PATH and NEKO_PATH are a thing btw - it's HAXEPATH and NEKOPATH (source).