I realize most people who are at this forum are probably younger than I (in my late 60s) and so the below may not be an issue. But great eyesight is not guaranteed at any age.
I already have to have my global Windows 10 Display scale setting at 175% on my 1920 x 1080 dual monitors. But even so, the project divider in Cubase 12 (I’m at current 12.0.30) has shrunk to a thin line compared to Cubase 11 as shown in screenshots below.
I used bright green areas to show each version’s respective area where on can drag the divider up or down. (And again, remember that this is on a system that is set at 175% visual scaling, so it will be even thinner for those closer to normal 100% scaling).
In short, it’s a strain to just see and drag the divider.
Perhaps this one issue could prompt Steinberg to consider at least fixing this change and other Preferences settings to make it easier for those with poorer eyesight.