How I can create a cross-reference to Bookmark in another file from LO dialogs. The way with copy Bookmark Name from first file and past here in second file seems to me as bad way.
Use Insert, Hyperlink.
Select Document icon instead of Internet.
Set the path to the other document using Open File icon to the right of the document path box.
Use Target in document, icon to the right of the target box. This only seems to work if the other document is not open.
Select the required bookmark from the list that appears in a new window to the right side of the hyperlink window.
Apply the selection and close in each window.