Thank you for reporting this. What you are describing (the browser slowing down heavily and freezing the interface) is a textbook sign of an unintentional infinite loop being triggered in your event sequence.
If the engine falls into a loop while waiting for the text input, it will freeze Microsoft Edge's script handler instantly, which explains why you can't delete the scene or why other elements seem to disappear.
How to fix it right now in version 1.9: Check the triggers around your text input action. Make sure the action that prompts the player for their name is triggered only once (for example, at the very start of a scene via a single "On Scene Start" event). If it's placed inside an event that continuously fires or loops, it will crash the tab.
For Version 2.0: The great news is that the upcoming version 2.0 completely rewrites how inputs and actions are queued. It includes built-in safe-guards that asynchronously pause the engine execution until the player explicitly submits their text, making it physically impossible for an input prompt to trigger an infinite loop or freeze your browser ever again!
Double-check your event triggers for that scene, and let me know if moving the text input to a single-fire action fixes the freeze for you!