It's all right, but where do we show Product categories in app? Since Product categories also attract users in the first place, where you have mentioned that the Re-order screen is the default landing screen. And there will not have any substance as a Product Menu in the app. I'm aware of this, that re-order for previous orders will be the main purpose of this app. And I do not wish to violate it in any way. But being a marketing manager and a senior mobile developer I think if it also can be added to the app, it will become a more complementary app. Also, I guess some of the benefits include increasing your sales and loyalty, and this can be done by bringing in your CRM data. Moreover, since there is a chance that it does not take much time to develop. As all product items classified in different categories will be stored into the web server and app will retrieve those through RESTfull API calling from the web server and show them accordingly. Additionally, we should have to navigate to the order screen(Payment) when user tap on any product item to order. So, as such in a way, we should have to make Product categories attractive to the user.
If you consider I would like to suggest if we can place a Product Menu button on the navigation drawer(left panel) or top-right to the navigation bar.
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