The XML Source help page lacks information that this is an experimental feature. I would test a file in a bug report but the Data > 'XML Source' menu item in Calc was deactivated (greyed out). In the web I found the info that this is an experimental feature and I had to activate that in the options. Other users, maybe one who don't know about experimental features, will hardly find this info or will know anything about experimental features. https://help.libreoffice.org/6.1/en-US/text/scalc/01/xml_source.html Suggestion: Add an info box that this is an experimental feature and a link to https://help.libreoffice.org/6.1/en-US/text/shared/optionen/java.html?DbPAR=SHARED#bm_id4077578 -- maybe with a warning that experimental features are not for average users due to crashes, the end of the world, whatever.
The note can be added with <embed href="text/shared/optionen/experimental.xhp#experimental"/>
Ilmari Lauhakangas committed a patch related to this issue. It has been pushed to "master": http://cgit.freedesktop.org/libreoffice/help/commit/?id=c6c0ddc60fec391d21a65b77b9b76066bfd0c2e7 tdf#120221 Add experimental note
Verified. Thank you!