Selfhosted

Have you checked nocode platforms/databases? It's basically a cross section of a super powerful excel and a database manager. You can set up the way you want, link records from different tables, add images, files to "rows", like excel on steroids. You don't have to understand SQL at all, that's why it's called "no code".

I use nocodb. Tried baserow before, but I didn't like that a lot of basic features are not available in the foss version, in nocodb only some bells and whistles are behind a paywall and not available in the self hosted version

They are also called airtable clones, as airtable was the first well known platform like these.

Some other similars exist: https://alternativeto.net/software/airtable/?platform=self-hosted&feature=database-management

You could probably approximate something similar with Odoo. It is a big ERP, but all modular, so you can just remove the parts that are too complex.

give erpnext and nocodb a testride

So...CCC seems to be a very basic inventory management solution. What this generally describes is a system compromised of a database with a front-ends that makes sense of whatever the particular project is (car repair), and provides an easy to interact with the database.

What you're using now is simply for workflow management of projects in a simplified way, which is probably not what you want.

So you need a database, and you also want an easy way to interface with it, so you can check out the plethora of inventory management solutions in the FOSS space, but if you want something pretty simple that you can more easily customize for your needs and workflow, have a look at the FOSS alternatives to Airtable like nocobase. You set up a simple data structure, then can slap together quick forms to work inside of with whatever fields and data you choose. Dead simple, but very extensible.

Edit: Also check out Baserow maybe