In tiddler edit mode, typing into either of the (new) tag- , type- and field- editors directly make the dropdowns display - great!
...so in what way do their respective buttons contribute?

I can only come up with one reason; to retract the dropdown... but this doesn't warrant a button:

• A user automatically, and immediately, disovers that the dropdown is retracted from clicking elsewhere (because the user has to click elsewhere in order to set focus to other elements - and this is even the case if the button is used for retracting the dropdown!
• If the purpose really is to retract the button, then its icon is misleading; it should be either an upward arrow or perhaps there should instead be a "x" button inside the dropdown to close it.

Could we cut out these buttons completely to lessen the already cluttery edit view? Is the 5.4.0 back breaker edition an opportunity?

BTW the immediate dropdowns also appear from keyboard jumping to the editors and the fact that the keyboard jumping skip the buttons are perhaps a futher indication that they are not needed?