Note 1: Changing a field's type from "text" to "masked" was a bit counter-intuitive. I kept trying to click on the ¶ symbol to change the type, which obviously didn't work. It took some time to figure out you need to select the field on the dropdown-section at the bottom, and then toggle its type and click the <type> button. A suggestion is to make it more clear and easy by just allowing users to click the ¶ symbol to toggle its type. However this is not essential - it does work quite well as it already is.
Note 2: The original request mentioned a "copy-to-clipboard" functionality. However when selecting (not editing) an item, There doesn't appear to be any way to copy-to-clipboard the value of a masked field (which is something you can do with URLs and passwords). You can click the <eye> to see it, but you can't do a copy-to-clipboard. It is necessary to edit the item, navigate to the field, select it, and manually copy it into the clipboard. This feature would be very nice, especially with secondary credential passwords, but but it isn't essential. It's just a bit more inconvenient without it.
Customer support service by UserEcho