It is allowed to resize the window so that part of the tabbar and some labels of the embedded dialog become invisible. For example, this is how Window Manager Tweaks looks like: https://i.imgur.com/NU92WKa.png

GtkTreeViews with Buttons need a unified look (inline-toolbar or not, button with icons+label or only icons, symbolic vs. colored icons, position of toolbar - horizontal vs. vertical)

On Focus and Settings tabs, some keyboard accelerators are highlighted by default. Doesn't happen when the dialog is run as standalone.

The horizontal scrollbar is shown initially but disappears on (any?) mouse click. The window becomes unscrollable: https://i.imgur.com/oGSb2WK.png

The top on/off buttons aren't aligned with other controls.

The “Default position” somehow doesn't affect the preview - it always shows in the top right corner, no matter what position is chosen.

The Notifications dialog tabs style (buttons) doesn't match other dialogs.

If I change Output from “Automatic” to “Primary”, the “Span monitors” checkbox becomes insensitive. But it never becomes sensitive again, even if I change back to “Automatic”. It takes reopening the dialog to make the checkbox sensitive.

If opening Panel from Settings Manager, there's no vertical scrollbar shown. However, when scrolling, the window scrolls but the scroll events also get applied to the controls inside the window: e.g., the Mode changes from Horizontal to Vertical, Output changes, etc. The panel starts jumping on the screen.

The overlay scrollbar looks weird: https://i.imgur.com/QZBIv6v.png