After upgrading to 23.4.2 (CU2) I noticed that whenever I open List Designer, it always loads one list. It appears that it is always loading the first list view in the list (alphabetically).
This is causing a delay in loading the webapp because this list contains a lot of data, and it is annoying to have to wait for it to populate every time when that is not even the list I am working on.
defect
This will be resolved in 23.4.3 (CU3).
For now, as a workaround, create a simple, small list with no data called something like "aaaaa", then this one will be the one that loads initially, reducing the delay.