Created attachment 435637 [details]
code for batch export

copy the content to Module1 (inside Tools->Macro)

1. Yes, OOo is always a single process, so if there is a non-headless instance already running, then a second headless is not created, so the -headless option doesn't affect the already running OOo that executes the macro.

2. No, it isn't stuck on a "Filter not found" dialog. Its the document is opened in writer successfully, the store to url fails, so it jumps to the ConversionError and the document isn't closed, so its still there idling.

Try this replacement code.

Created attachment 435749 [details]
replacement code

This might work better

Caolan,
Thanks a lot. The code you suggested works fine with invalid content inside input file.
The only problem left - if input file does not exist at all.
Then I get an error (and window opened) and stuck at
 oDoc.close( True )

I tries the handling below
----------------------
Sub SaveAsHTML(iFile, oFile, convertername)
   ON ERROR GOTO ConversionError
......conversion code....
   ConversionError:
   ON ERROR Resume Next
   oDoc.close( True )
   'exit sub
End Sub
------------------------------

but the result is the same - if input file does not exist -
the new window is opened and oDoc.close( True ) is highlited.
I can do a workaround to test file existence outside of OO,
but would much prefer to handle oDoc.close( True ) errors in basic.

I fixed mentioned problem this way, is it correct?

Sub SaveAsHTML(iFile as String, oFile as String, convertername as String)
   ON ERROR Resume Next
   Dim oDoc As Object
   oDoc = StarDesktop.loadComponentFromURL(ConvertToURL(iFile), "_blank", 0, Array(MakePropertyValue("Hidden",True),MakePropertyValue("ReadOnly",true),))

   if IsObject( oDoc ) Then
     oDoc.storeToURL(ConvertToURL(oFile), Array(MakePropertyValue("FilterName",convertername),))
     oDoc.close( True )
   EndIf
   'exit sub
End Sub

looks fairly reasonable