How to remove read only

I am trying to delete
part of my document but I cannot because it is read only. How do I remove read only?

Ctrl+Shift+M ? Menu Edit - Edit Mode (last position)

I had the same issue on Mac OS with OpenOffice. I would uncheck the Locked option to no avail. Several documents had this issue. As a test I made a copy of the document, which was therefore named XXX copy.odt and I could work on it with no problem. So I trashed the original and renamed the copy XXX.odt… which became locked too. I moved the document to another folder and it was unlocked but when I moved it back to its original folder it was locked again.

Someone told me that OO radomly creates an invisible sidecar file that makes the file locked. So either you manage to display the invisible files and trash them or you move the document(s) to another folder and trash the original folder. It’s what I did. LO may have the same issue.