The workspace UI needs an overhaul. If you look at the first screenshot attached, it is for example not clear which icon is the active one. In previous versions of Notes there was a more clear depression of the chicklet, Now it is all flat. I know that flat UIs are the popular thing at the moment, but it should not be done in a way that makes it harder for the user.
Much of the complaints about Notes from users has revolved around the UI. Making an attempt to modernize it is good, but there is much left to do. A total redesign of the workspace is long overdue.
Look at the second screenshot, just by fixing the icons it already looks better. Flat does not have to be boring.
Make the workspace skinable using CSS, or some kind of editor. That editor should be able to export the design/theme as JSON, and it should also be possible to load that JSON into the editor. That way users can exchange themes. Include the background image as B64-encoded data.
Allow different colors and backgrounds on each chicklet. Also allow rule-based backgrounds/colors for chicklets. For example, I use an icon with red background for all my .NTF templates, and the same icon with transparent background for the corresponding database. It would be great if I could set that color automatically, using a rule-based background color. Then the whole chicklet would be colored, not just the icon.
Adding folders, so icons could be nested within a tab. I know you can add as many tabs as you like, but you want them all to be displayed in teh window, not having to scroll, perhaps forgetting they are there.
I do personally not like the new look of the tabs, they are too square and pointy. Also, the text on active tabs is hitting the edge of the tabs at full length, while there is a lot of empty space when the tab name is short. The tabs should resize and fit the label better.
There are many little things like that that could improve the workspace a lot. Put a design team on this, and see what they can come up with.