Like the new instrument window, it should be possible to resize and (more important) minimize the window of a tool.
E.g. I have often two or more tools on the screen to edit some data; I have always to drag them to another place when using the pattern editor (the tool’s windows hide some tracks of the pattern editor), or even close and restart them with the tools-pulldown menue, which is not comfortable and slows the workflow.
I dunno… LOL, because the new instrument window is my one complaint about the GUI.
In all the versions of Renoise that I have used, the instrument box is pretty stationary… Now, I really am not used the effect of the box sliding and morphing shape depending on whether the browser is opened or closed.
I do like the instrument window vertically sliding down… 
/>/>/> that’s a good feature.! I just do not like the way it morphs when you slide the browser all the way over to the right 
Edit = my skills with the mockups are virtually non-existant but this is the GUI thing that I thought might be a little more consistent throughout the versions…
