Libre office change default save format via gpo,reg,bat,

Hi, looking for any free way possible to change default save format for writer and calc via gpo,reg,bat.

So you don’t want Tools > Options > Load/Save and select the default file type under Default file format and ODF settings?

You are best off saving in Open Document Format (ISO Standard), that way you will have fewer problems as other formats might not support all options offered by LibreOffice. See
Tutorial Differences between Microsoft and AOO/LO files. If you need to send a document in another format, just Save a copy