I want to add multiple products and also set up deposits for all products at once

Depo provides a feature called Import Collection where you can import multiple or single collections at once and then provide payments for those collections. You can also update multiple part payment options using the same feature
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Please head over to Depo > Partial Payments > Import Collections to start the import process. Once the items are imported you would see a pop-up to set up the Deposits configuration for all the products.
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