When using "Save as" in Editor.'s pulley message, and then tapping on file in the file chooser, the focus should jump to the text field (with the cursor placed at its end) and consequently the keyboard activated, as the key in the lower right corner of the virtual keyboard is the only way to affirmatively exit this dialogue, anyway. Currently one has to explicitly tap on the text field after tapping of an existing file in order to proceed.
One could still tap on a different file or swipe vertically in the file chooser below to refocus the file chooser section, then.