In ArcGIS Pro, several application panes appear something like this:
While the pane is small in size, there are benefits to keeping it small, such as on a small screen or when performing detailed design work. There is lots of negative space and missed opportunity for the alignment of dropdowns and location of buttons. This design requires a massive amount of scrolling or frequent adjusting of the pane size to get anything set the way you'd like, which is one of the core inefficiencies of this software.
A concrete suggestion I have for improving these interfaces and thus the productivity of the software is to resize and align dropdowns, tables, and other toggles so that they are aligned at the right of the pane regardless of size. It appears now that they are set a fixed distance from the left, which only works well for a pane of a particular size. Scrollbars, when absolutely necessary, should be kept from overlapping the controls.
Another way to improve the use of space might be through icons. Many items, such as "font name" and "font style" could be replaced with icons, as the dropdowns are fairly indicative of what they are. Other options, such as Underline and Strikethrough, could be replaced with toggle buttons entirely and placed in a row. There are a lot of opportunities for space-saving, intuitive design that enables muscle memory, less scrolling, and speed.
One good example of the desired responsiveness to size are the panes in Adobe Illustrator, which are actually modular panels and thus beneficial for muscle memory. They involve less scrolling and less wasted negative space to begin with. Some panels (such as color and layers) are beneficially responsive to size when absolutely needed:
Areas that have something to expand (text, color) do, while keeping controls where you'd expect them.
But we don't need to look outside of Esri software for a good example - ArcMap's windows have a smart, efficient, and consistent placement of controls. Adapting this approach to the pane context and responsiveness to resizing would be a huge, huge step for productivity in ArcGIS Pro.