I don't believe that the pop-up to choose your file is a web element. Unfortunately, you will not be able to interrogate this control as it's not supported out-of-the-box in chrome.

However, we have been able to interact with this type of controls through a C# script that uses UI Automation to find the controls such as the combo box and buttons and perform actions on them. If you are unfamiliar with UI Automation there are some good examples on the Microsoft website. This is a good place to start:  https://docs.microsoft.com/en-us/dotnet/framework/ui-automation/ui-automation-fundamentals