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I'm from Germany and I build similar systems for some customers, for example a tenant management tool.
I would like to build that tool for your design management. I would use PHP, Bootstrap and a MySQL Database to build a responsive web portal where you can manage your designs. Bootstrap makes the portal responsive and you can use it perfectly on tablets and phones, too. The Bluehost Webspace would be perfect for hosting this.
I would build a section to view designs, with search, filter, sorting (priority, etc.) and editing and another section for adding new designs.
The portal will be secured with a login. If you need, we can add special "admin" accounts, which can create / edit users. Alternatively every user could edit users, if you trust your co-workers. ;)
If you have enough webspace, we could upload your designs to your webspace, and view them in the portal, that isn't a problem.
If you like, I could import your existing designs from your Google Drive / Sheets to the new platform!
I hope you like my offer, thanks!