When I save as a .docx and re-open a Writer document, the lines that I have inserted using Shapes, anchored to the page have moved to a different location. Using Libreoffice in Win 10. How do I keep this from happening?
You don’t tell under which format you save your file. If this is .doc(x), there’s a high probability that your shapes move because Writer and Word have a different idea of what a page is. You don’t tell either how your shapes are anchored (page, paragraph, character) and their wrapping mode. You give no indication on the procedure to position your shapes.
Edit your question to provide this information, LO version and OS. Note that answers are reserved for “solutions”.
What happens if you save as .odt? Are your shapes still where you put them in the first place?
With .odt, you spare two conversions: one to export to .docx and the second to import from .docx. Every time ou go through a cycle, you create new discrepancies (at least until information loss settles down to a steady state). In any application, work in native format until the very last step where you’ll export to delivery format and fix the issues in this format (if possible). Unless you’re in collaborative context, there is no interest to use .docx and even in this context, M$ Word is supposed to read .odt files. So, you’ll be able to put the blame on Word for not abiding by the ODF standard.