Edit to original post: Strange cursor in libreoffice 6.2 pc windows 10

edit

This is Direct Cursor Mode, in which clicking in any place in a document allows you to write there - by adding sufficient amount of empty paragraphs and spaces/tabs as needed:

Its operation is configurable at Options▸LibreOffice Writer▸Formatting Aids.

I'd say very bad tool; and combined with disabled formatting marks, it is guaranteed to create a mess in your document.