Using portupgrade produced silly erroneous error message:
! editors/calligra (calligra-2.9.11_11) (unknown build error)

However going into the port directory it built 3.0.1 without problem.
I am impressed with the build. On seeing that 3.0.1 seem to be building nicely I did delete 2.9.11

However, on opening Calligra Words,
the font-size in the side menu seem to be about double what they should be.

Same thing with Sheets and I presume every other Calligra application.

Hmmm, I'm not an expert but I think fonts are handled by qt. Calligra 3 uses qt5 while 2.9 uses qt4.
Could this be an issue?