Custom Shopify-Integrated Inventory Management System

I am looking to build a clean, structured inventory and operations management system for my brand, integrated with Shopify.

Let me explain my current situation:

I sell products both online (Shopify) and through consignment stores (where stores take 50% commission). My inventory is distributed across multiple locations (warehouse, different stores, etc.), and currently a lot of tracking is done manually, which is causing inconsistencies and errors.

I need to move away from manual tracking and build a centralized, automated system.

What I need (System Scope)

I want a system that includes and connects the following:

Products

Inventory (with multiple locations)

Stock movements (transfers between locations)

Sales (Shopify + manual consignment sales input)

Orders

Customers

Suppliers

Collections / product categories

Consignment tracking (including store commission splits)

Key Requirements

Centralized system
One single source of truth for all data (not fragmented across tools)

Inventory tracking across locations

Track stock per location (warehouse, each store, etc.)

Easily move stock between locations

Every movement must be recorded and automatically update inventory everywhere

Consignment management

Track which products are at which store

Log sales coming from stores

Automatically calculate revenue split (e.g. 50% store / 50% us)

Shopify integration

Sync products and inventory

Reflect accurate stock levels

Avoid overselling

Automation

Minimize manual entry

Changes in one place should reflect everywhere

Clean workflows for daily use

Clarity & reporting

See stock levels per location at any time

Track sales performance (online vs stores)

Track profitability

Preferred Approach

I am open to different solutions, including:

Shopify-based system (apps + extensions)

Airtable / Notion with automations

Google Sheets + automation (if robust enough)

A lightweight custom system (if necessary)

The priority is simplicity, reliability, and scalability.

What I need from you

Recommend the best system architecture

Build and set up the system

Integrate with Shopify

Ensure it is easy to use daily without errors

(Optional) Provide a simple SOP / user guide

Important

This should feel like a structured business system (similar to a lightweight ERP), not just a basic spreadsheet.