Make sure you click the add attachment button after browsing to it 
As for the issue, you're probably running a 4k screen (or multiple screens and at least one of them 4k) and have windows scaling enabled in your windows setting right?
Some machines depending on the setup and OS do not properly do the windows scaling, and unfortunately I don't have access to a problem machine like that in order to test and fix that rare edge case (for example, on my own 2k and 4k monitors, the scaling works fine and the sidebar isn't cut off). So I added a setting in the Debugging rollout of tyFlow to manually expand the width of the operator sidebar. That setting is also sticky so you only need to set it once and it should load that setting each time you re-open the editor. So try that and let me know if it works.
As for the issue, you're probably running a 4k screen (or multiple screens and at least one of them 4k) and have windows scaling enabled in your windows setting right?
Some machines depending on the setup and OS do not properly do the windows scaling, and unfortunately I don't have access to a problem machine like that in order to test and fix that rare edge case (for example, on my own 2k and 4k monitors, the scaling works fine and the sidebar isn't cut off). So I added a setting in the Debugging rollout of tyFlow to manually expand the width of the operator sidebar. That setting is also sticky so you only need to set it once and it should load that setting each time you re-open the editor. So try that and let me know if it works.