IntelliJ IDEA
IntelliJ IDEA – the Leading Java and Kotlin IDE, by JetBrains
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Tutorials
More Flexible Toolwindow Layout in IntelliJ IDEA 8
A little-known new feature of IntelliJ IDEA 8.0 is that it allows you to have two docked toolwindows visible on each side of the screen. So you can, for example, view your changes and your TODO list at the same time at the bottom of IntelliJ IDEA window.
In order to configure this, you need to use drag & drop — for example, to view the TODO list in the right part of the bottom area, you should drop its button to the bottom right corner of the screen.
I have recorded a short screencast showing how this can be done: