Does anyone know how to fix an issue with a multiply map that has a transparent background, where it's barely visible in-game? I have to get extremely close to the model to see the outline of the texture, but if I move away even a little, it seems to disappear completely. I've tried adding mipmaps to the multiply map, but nothing changes. Up close, it looks fine in-game, but it's supposed to appear the same as it does in Blender.

Are you editing this item in TSR Workshop after doing the mesh in Blender? If yes you can chance Fresnel offset to lower number (default is 0,5) - this manipulate how bright the item appears on different angle (or sort of), change shininess to lower number (default is 20) and if there is a separate mesh group for the deer's body you should try to darken the specular map a little.

By the way your item looks great and so pretty 💕

Edit: it's not good idea to make the multiply map fully transparent. Put some color - black or grey with low opacity.

You should always export with mips, anyway. The easiest way to figure it out for certain, would be for you to upload your work files to be looked thru. Not having that, from seeing the tris pattern, it looks like you either exported the UV map, or exported as png?

If you're using NVidia Texture Tools exporter, make sure to scroll down and tick Scale Alpha for Mipmap Coverage.
Fine transparency details are easily lost on mipmaps.

The deer is meant to be a Christmas decoration, and rather than using a high-polygon model, I baked a texture in Blender with the wireframe node. That’s why the multiplier map needs to be transparent—to give the deer a wireframe appearance. In the NVidia Texture Tools exporter, I always enable "Scale Alpha for Mipmap Coverage" when generating mipmaps. I suspect the issue is texture-related, so it would be helpful if you could take a closer look at the problem.

My theory why your deer's body seems invisible in game because the mesh net that wraps it around has very thin lines that can be seen by the game as some sort of aliasing and the the edge smoothing/anti-aliasing setting tries to clean it (sounds stupid but it's possible).

You should try to make these lines thicker with several millimeters or use another type of DDS compression and see if anything has changed.

You also can try to place a background color layer to the multiply map image that is darker with low opacity.

What did you use for your donor? I think I see a couple of issues, but I can't replce your mesh in TSRW. Anyway, what I see is the alpha channel of your multiplier is gray in areas of the deer body, which means it's transparent. Not sure that will work with phong shader, which is a transparency shader. In GIMP, I added a layer mask (from image), and increased contrast until all the lines showed white, which is a solid line. Then applied layer mask. Then, I evened out the multiplier gray scale by reducing contrast. Some of your multiplier wwas white, which I also don't think will hold color on phong shader. I'm not an object creator expert though!!!!

Final thing is that a phong object would need backfaces, similar to hair, or you only see one side, and looking thru the deer, you won't see the wwireframe on the oppositie side. I hope you understand what I mean.

I've heard about the foliage shader, but no experience using it. Might have been @Cardinalsims who told me about it? I wonder if you apply that shader to the deer body, it will show the backsides, without adding backfaces to the mesh?

I've seen that the mask you've made is probably for four recolorable channels, right?
Whenever your mask is for four or less recordable channels you should use only solid colors without shodows/highlights. For example for three recolorable channel mask RGB every - red (255, 0, 0 on RGB palette), green - 255 for green and blue - 255 for blue. Not familiar with 4 recolorable channels but yellow must be combination between solid green and solid blue.
For the blank area (that is not covered by anything in the UV map) I just fill it with other color black for example. According to me leaving transparent sectors in the mask is wrong.
The mask is probably related to the problem too, also with the things LadySmoks mentioned in previous post.

Okay, I will look into it.