Two editors have commented independent in different place over the weekend on English Wikipedia about how they wish they could access the edit summary while using the VE instead of on save, because they track their changes as they go.
Version: unspecified
Severity: enhancement
Think this is also happening on PL.WP.
"Jeśli w okienku z polem służącym do opisu dokonanej zmiany klikniemy w link dotyczący sposobu opisywania zmian zostaniemy przekeierowani do strony Wikipedii z opisem tychże skrótów, jednak strona ta wyświetla się w tym samym małym okienku. Uniemożliwia to powrócenie to opisu modyfikacji a jednocześnie uniemożliwia zapisanie dokonanej zmiany w danym artykule. Michał (dyskusja) 11:36, 5 lis 2013 (CET)"
https://pl.wikipedia.org/wiki/Wikipedia:VisualEditor/Opinie#B.C5.82.C4.85d_w_okienku_opisu_zmian.
On a related note: There's also no edit summary in the diff view ("review you changes"), just a save button. This tempts users to save without leaving an edit summary.
(Although they won't be able to do so if they enabled the warning that doesn't allow to save without providing an edit summary, as noted at de.wiki. )
@Sadads has suggested that the Tab key be used to switch between the article and the edit summary window.