If it helps, do know that I fully agree with your request and I see it as a high priority.
The IDE is heavily based on Microsoft .Net WPF + other powerful .Net UI libraries. These technologies are Windows only.
The current IDE is (very) good. It has good performance, it is flexible and it fits B4X like a glove. I don't want to invest a lot of time and efforts to build a new cross platform IDE that will be eventually worse than the current one.
Microsoft is pushing to make .Net cross platform. This might open new possibilities.