While the Custom Property Editor in 10.4.1 is a welcome improvement, it still needs some work. I have found that editing properties that have a pull-down selection list only seems to work intermittently. The pull-down button appears, and you can select a value, but it goes blank after you move to another row.
We have found that you can increase the number of rows to a maximum of 500. It took some trial and error to find the max, since the error message only says "invalid page size" and doesn't say what the maximum is. It does turn the value red, and if you hover it tells you the maximum, but I didn't discover this until I tested several values. Not a big deal I guess.
It would be nice if you could reorder the columns and have this stick between uses. That was my one complaint with the old custom property editor. And have a Default button to return it to alphabetical order. (note I like it in alphabetical order instead of database order like the old tool).