I work in OOo a lot, but often need to keep a copy in MS Word (Excel, whatever)
for colleagues to open.  To dump a file in PDF I have the export button, there
is also a function "Email as MS Word document", but there is no "Export to MS
Word" function.  I can use a Macro to "Save As", but then all subsequent saves
happen in Word format and not in .odt.

Export (the button which can be added to the toolbar) does not allow all
formats.  Easiest would be to allow exporting to all formats allowed under Save
As, then a macro can be created to Export to MS Word or whichever format is needed.