From your store's own orders: every order with two or more products tells Takmila they were bought together. After install it reads your last 6 months of orders, then learns from every new order automatically. It favours products genuinely tied to each other over bestsellers that land in every basket.

Yes. Until there are enough orders it can suggest products from the same category, and you can pick any product's suggestions yourself in the app's dashboard. You can also lower “Fewest shared orders” to 1 in the settings.

On product pages under add to cart: the product with what's bought with it, with checkboxes, the total and an “Add all to cart” button. And on the cart page: “Complete your order”, with an add button per product. You can turn either off in the settings.

The product on the page is added with the shopper's own choices through your store's button; if a size isn't chosen yet, your store says so. Suggested products that need a size or colour show a “Choose options” link to their page instead of being added without one.

Yes. In the app's “Suggestions” tab, search for any product to see what customers buy with it, pick up to 3 products to show instead, or go back to automatic whenever you like.

From the Salla App Store: billing, the free trial and cancelling all go through Salla.