cannot uninstall MasterDocumentTemplateDR.odm extension

After installing the extension, it did not appear in the extension manager nor in templates. However, upon executing File->New->Master Document, a new Master Document opened. I did not like it, so I tried to un-install it. In desperation I deleted the .zip file

Now get a blank document (ok), but occasionally the old master document image appears and messes up the display. When i click on it, it just vanishes. Where is it hiding? How do I get rid of it?
P.S. I am running LO 5.1.6.2 on Ubuntu 16.04 with the Xfce 4.12 desktop environment.

What is “MasterDocumentTemplateDR.odm extension”? Where one can see it?

Open LibreOffice writer. Tools->Extension Manager… This opens the extension manager dialog. At the bottom click on “get more extensions online”. This opens the “Extensions & Templates” web page (https://extensions.libreoffice.org/). In the search Site box, type “master document”. A drop down list will show “A Master Document”. Clicking on it takes you to the extension page. Download the .zip file and extract the contents. Run the ,odm file.

This is just another document file you can create or download. It’s not an extension, and doesn’t “install” anywhere. It’s not even a template!

If you have done something obscure, and have some strange results, you may want to try to reset your LibreOffice user profile.

I examined the advanced user profile, which I did not know existed. No values were set, so I did not want to meddle with it. I stopped experimenting with a master document and subsequently have not experienced the problem I have described, but the cancer must still be there. Thanks for your comment.