I wanted to do some editing of the photo I've taken off my phone before uploading to Instagram. To my surprise, the web version of Instagram does not offer this feature.
Short of using a third party tool to do it, the work-around is to use Chrome browser's developer's tool to fool the web-app to think we are using a mobile device.
For instructions go to : https://www.forbes.com/sites/tjmccue/2018/08/30/how-to-post-on-instagram-from-pc/
All it require are 4 steps. Good luck