The file_open standard action should always appear after file_new. This
is not the case in the Kate toolbar, where we have Open before New.
This happens because there is a custom file_open group that breaks the
kxmlgui merging index (the file_open action gets 0 rather than 1).
This was introduced a long time ago with:
https://websvn.kde.org/?view=revision&revision=350820
The log message just says
"to allow the template plugin a button in a relevant position"
which is probably no longer relevant. Dropping this group makes Open
appear in the toolbar after New, as expected.