I found that Yakuake was re-opening with an 80% width and about 30% height but I prefer 100% wide and 80% high. So it looks like my settings were saving into the file:
~/.config/yakuakerc
But this was possibly not the file that was being read when Yakuake started. I added the
[Window] Height=80 Width=100
entries to the file:
~/.kde/share/config/yakuakerc
And it worked as I wanted YMMV
