LibreOffice 6.0 unzip - zip open document file?

In LibreOffice 5.0 I used to be able to open an Open Document file (e.g. *.ods or *.odb) on a low level by unzipping it. Then I could change something there on the “low level”, zip it again and use it. I used the Ubuntu archive manager to do that. Since Ubuntu 18.4 and LibreOffice 6.0 this does no…