Wish Synth block Pitch Portamento

[Six String Symphony]

I do like the synth block even with its simplicity. However I had an idea for a patch and wanted to add portamento to the pitch tracking. Since that parameter is missing I did a couple of workarounds that almost worked perfectly. But in the end I cannot get the pitch of each 12 notes in equal temperament to happen with those alternate approachs. Please add a portamento or pitch slew rate control if possible.