I can't follow this step:
> Add an action by clicking "add action", while pressing CTRL+S at the same time (IMPORTANT: finish the process of adding an action!)
How do you do these two things at the same time? Construct does not let you. When you click "add action" a modal dialog appears, which prevents saving. Once the modal dialog is closed, you can save again, and that seems to work correctly.
I tried to reproduce this in r272 but there is no error message. I will try to reproduce this again in the next beta cycle, since there have been a lot of updates.
The reproduction in general is very precise and you have to press CTRL+S just a few milliseconds before clicking "add action". Again, I'll try to reproduce this and upload a video of it happening in the next beta cycle.