Robinhood is quite unique when it comes to tax reporting for a couple of reasons. When it comes to filing your capital gains from Robinhood, you have two options:

Edit 2022: Robinhood now allows users to send and receive crypto. If you have deposited or withdrawn crypto from your Robinhood account then we would not recommend this option.
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Usually, you should always import all of your different wallets to Koinly but Robinhood is one of the few exchanges that can actually be excluded from Koinly.
The reason for this is that Robinhood does not allow any crypto deposits or withdrawals so all of your Robinhood activity will be isolated on the Robinhood platform and can therefore be tracked separately. Robinhood also provides a 1099-B tax form that can be used directly when filing your taxes so it's often easier to report Robinhood separately and use Koinly for all of your other exchanges and wallets.
If you chose this method then you will essentially end up with two tax reports, one from Robinhood and one from Koinly.
This method is recommended if you are not able to get a transaction history from Robinhood or if you have traded anything other than cryptocurrencies on Robinhood (such as stocks) since Koinly will only be able to track your crypto transactions.

Robinhood does not have a way to export the transaction history which makes importing your transactions to Koinly a bit tricky.
There are a few options available such as creating a custom CSV file or using an alternative method to extract the transaction history, such as a transaction downloading tool (this involves using third-party tools or apps so please be cautious).
If you do manage to get your transaction history or create a custom CSV then you can import this to Koinly to include your Robinhood transactions in the Koinly reports. If you do this then you should not use your 1099-B form for tax reporting since those disposals will already be included in Koinly's calculations

This is because the 1099-B is essentially a tax report but Koinly requires your actual transaction history. The 1099-B only contains your disposals but not the full transaction history

That's a good question but, unfortunately, we do not have the answer. It is a strange limitation of their product as it has been a highly requested feature for many years. We do hope that Robinhood adds this feature soon.

The Robinhood API seems to work quite well but it has not yet been publicly released. The main issue at the moment is that it would require users to give Koinly their Robinhood passwords as there is no way to generate read-only API keys for the API.