I cannot make ArcGIS Pro use all available vertical space in the first column of the legend before wrapping items to a new column. Multiple items will wrap to a new column at once, not on an individual basis. Even though sufficient vertical space is available for a legend item, it will still insist on wrapping to a new column. Some of the legend items appear to behave as a group, even though they are not in the same feature class or grouped in any way.
If I increase the legend height incrementally to allow space for one or two additional legend items, nothing happens until the vertical space is large enough to fit all legend items, and then they all wrap together.
This first picture shows the extra vertical space where I would expect, at the least, the "Concrete Containment Berm" layer to stay in the first column rather than wrapping to a new one.
The second picture shows the height increased to the minimum level to make the "Concrete Containment Berm" layer wrap, at which point all other legend items wrap with it. No middle ground.
A few more details:
This does not happen in ArcMap. Vertically resizing the legend will use all available space in the first column before wrapping to the second.
Any ideas on how to fix this are appreciated.