Start this project, then go to https://scratch.mit.edu/projects/678891277/ and type something. After 5-10 seconds, this project will detect that the other project is sending a message to it, and it will take roughly 4 seconds on average for each character to be sent to this project. Note that this could be inaccurate.
This does not use cloud variables. Disclaimer: Nobody other than you could receive the messages, so this is not a chat project. The messages are stored locally, on your computer. Credit to https://scratch.mit.edu/projects/678405307/ by TimeTravel2022 and https://scratch.mit.edu/projects/678420788/ by Retr0id for inspiration