Which Umbraco version are you using?
15.3.1
Bug summary
In earlier versions of Umbraco, the split-view feature worked fine on smaller of screen sizes. However, in Umbraco 15, when using a Block List, the split-view only displays correctly on ultra-wide screens. For reference, the image below shows the layout on a screen with a width of 1720px.
I’ve reported this as a bug, as it doesn't appear to be the intended behavior. Based on current testing, a screen width of at least 2400px seems to be required for the split-view to render properly.

Specifics
No response
Steps to reproduce
See above.
Expected result / actual result
No response