I’m looking to automate this process—specifically, to add accounts and obtain tokens programmatically instead of manually

I’m managing my clients’ accounts and would like to automate the process of posting content using the Instagram Meta API. Currently, when I create an app on the Meta platform, I also add the "Instagram: Allow creators and businesses to manage messages and comments, post content, and monitor insights, hashtags, and mentions" product. However, during the "API Setup with Instagram Business Login" step, I need to manually add accounts and obtain tokens.

I’m looking to automate this process—specifically, to add accounts and obtain tokens programmatically instead of manually.

The steps I’m encountering are shown in the image below:

The solution you are looking for involves a level of scripting that will inevitably put your clients' accounts at risk of being flagged or banned, so be very careful.

Since your app is un-reviewed, your best bet is setting up a business login flow (point 3 in your screenshot) and manually add your clients as testers before logging them in.

The Instagram docs explain the limitations of this approach really well. Once your app is reviewed and approved, your clients can authenticate directly without those extra steps.