Comment 8 for bug 1879479

László Németh committed a patch related to this issue.
It has been pushed to "master":

https://git.libreoffice.org/core/commit/cf596c43315bb96b5e7256a82256f1ccb8c9c4d0

tdf#133163 DOCX: export formula cells

It will be available in 7.1.0.

The patch should be included in the daily builds available at
https://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More
information about daily builds can be found at:
https://wiki.documentfoundation.org/Testing_Daily_Builds

Affected users are encouraged to test the fix and report feedback.