I didn't get a chance to participate in the beta so I don't know if any of this is addressed or planned, but I have some thoughts.
Some way to visualize multiple rooms at once, so that I can more directly see where my exits and endings are leading the player would be really useful. Yeah, this is already shown in the endings and exits tab, but being able to see multiple rooms, even if it was just a few at a time, would be very useful to a person like me who sometimes has a hard time visually connecting things in rooms I'm no longer looking at. Kind of as an extension to this: the ability to "stack" bitsy windows might be useful in this regard. Instead of just placing colors next to paint, next to the room editor, etc, you could put paint underneath colors or have download tool resting over the game data window. This kind of organizational grid setup would allow users to further customize their bitsy workflow and, for me anyway, would limit the amount of time I spend opening and closing tools and manipulating a scroll bar.
Finally, dark mode please. I am a vampire. The cozy blue background is very nice, but sometimes causes me eye strain.
Maybe these things fall more in line with a module/extension that someone could make later on, but I figured it doesn't hurt to ask!
Keep up the incredible work. I legitimately don't think I'd have gotten as passionate about making things again if it weren't for bitsy. I'm very excited for whatever the future holds for this project.