Never work in foreign file formats. Never store your important documents in a foreign (and/or obsolete) file format.
Always use the native, international standard (ISO) ODF file formats for your documents.
And at the end of editing you can save/export a copy of your important documents into the desired foreign file format - if it is necessary.
Note: There is not (never was and never will be) 100% compatibility between the different file formats. You always will lose some formatting property at every conversion. And an opening/saving procedure always means a kind of conversion, because the LibreOffice can work with an ODF model only.
There are third party extensions for the Munltiformat save. They can save the documents into more than one file formats in same time: