Need help with preamble pathing

Question

In my main.tex I am requesting my preamble to be loaded through the command \usepackage{preamble}, which is in the same folder as my main.tex. My subfiles are located one folder below, e.g. MAIN/introduction/introduction.tex.

I would like to compile my subfiles as individual documents as well, but I get the error preamble.sty not found, which I presume is because I do not have a preamble.tex file located in my subfile folders, only in the main folder.

Is there a possible way around this? For example, would I be able to specify two paths for my preamble, e.g. \usepackage{preamble} when I am compiling my main document and \usepackage{../preamble} when I am compiling my subfile?

Thanks for the help.

EDIT:

My preamble is in .sty format, and I load it in my main.tex with \usepackage{preamble}. I am unable to write the same thing in my subfile document because AFAIK the layout of a subfile has to only have \documentclass[main.tex]{subfiles}. Otherwise, I would also write \usepackage{../preamble} in my subfile document.

My folder structure is as follows:

main_folder/
   preamble.sty
   main.tex
   introduction_folder/
       introduction.tex

When I compile main.tex with \usepackage{preamble}, it works just fine. When I compile introduction.tex, I get the error that preamble.sty not found, even if I add \usepackage{../preamble}. I am using the subfiles package to create my subfiles.