Cascade High DPI bug - No (no proper) horizontal scrollbar in emitter tab

On a 4K monitor with high DPI support enabled in the Editor some issue will occur with scrolling in particle effect emitters. This causes some of the emitters to get cut off completely and unable to be selected in editor. 

Dragging the editor over to a 1080p monitor instantly makes the scrolling work as normal.

1. Go into the Editor preferences and ensure that High DPI support is enabled.
2. On a 4K resolution screen with high dpi enabled open a particle effect.
3. Make sure particle system has enough emitters that causes a scroll bar to appear to navigate them.
4. Play around with scrollbar and location of the emitters tab.
5. Notice that the scroll bar will not scroll through all the emitters.

This works fine in 4.18 but 4.19 and 4.20 are showing this issue.