Apply shader to a group of sprites as a whole

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:bust_in_silhouette: Asked By TheJokingJack

I have an outline shader that applies an outline to a selected sprite. What I want to do is to apply that shader to a group of sprites as one singular entity, if that makes sense. Basically, the shader would outline all sprites within the group, but not the areas that overlap.

The closest connection I can make is for digital artists. Have any of you ever used Krita? If you apply an outline “stroke” to a group, the stroke outlines only the edges of the group that it makes as a whole, and not the individual layers.

My question might be harder to understand, so here is an image: Example.png - Google Drive
(the image on the right is what I wish to achieve)

Thanks to anyone who offers help!