Using Libre Office on Mac Catalin
I open and create LO files through the LO window that shows previous created files. If I save the document to a folder it automatically saves and reopens as Open Office which changes the formatting when photos are included in the document. If I rely on the LO window to store the completed documents after a time the message comes up that this file does not exist despite the image appears on the screen
This means you don’t use frame styles and applied direct formatting, even as innocuous as moving the image or resizing it with the mouse.
The “Start Center” is a passive cache (recently used documents) which is not updated when you manage your files outside LO. LO has no way to guess what you did to the listed files and can only tell you that the cached path no longer correspond to a document.
Do you mean that you have both LibreOffice and OpenOffice installed on your system; and that in some directory, the files get opened by OpenOffice?
I am not a macOS user; but if I remember correctly, there is a way to set up file associations per directory on that OS. But then, it’s not a LibreOffice question, but something about your OS usage.