See attached screenshots. In both cases, Qt Creator 9.0.0 is launched directly on the secondary screen which has 200% scaling. QtC is launched after the primary screen's scaling has been set.

• When the primary screen is set to 100% scaling, QtC looks good.
• When the primary screen is set to 125% scaling, some elements become far too big (Sidebar, top-level menu, Locator input)

Notes

• Single-monitor setups with fractional scaling are also affected.
• I used the setup above to make it easier to compare good vs. bad outcomes.