Creating a tab for each manufacturer is the problem.
Normally, the following approach works much better.
Create one worksheet that contains all of the manufacturers. There should be one row in the worksheet for each manufacturer.
The first column in the worksheet should be the ManufacturerId key field that uniquely identifies each manufacturer. I normally use a text field and set its InitialValue to UNIQUEID(). If you already have a key value that uniquely identifies each manufacturer, use that instead.
Create one column in the worksheet for each property you need to store for each manufacturer. For example,
you might have properties for address, phone, email, etc.
The idea is to create one worksheet (and hence one table) for each type of thing you are keeping track of in your app. For example, you might create one worksheet per Manufacturer, another for Orders, another for Products, etc. You then use References to link the records in your tables.