Rant.
I called phone support and we spent 1.5hr on this issue. We went thru all the MA and OR questions again (assuming I missed the question which allows to specify how much short-term capital gains should be attributed to MA), but failed to find it.
Agent asked multiple times to verify if my Windows is updated. In the end Agent was out of ideas and suggested me to restart Turbotax tomorrow and see if it updates and maybe my issue will be resolved. That suggestion made me speechless for a moment.
After I've been pushing back, agent agreed to check with his supervisor if this is an on-going issue and they might have answer to that question in a week. Agent refused to escalate this issue further, despite together we failed to find how this could be a user error and it appears to be Turbotax error.
All tools have issues, that's ok. But how company manages these issues is what matters. In this case Turbotax failed completely. I do not remember when I had such a poor experience with support. I've been using Turbotax for the last 10 years, this year is the last one I use it.
Solution.
Staring at the same forms again I discovered that any field in the form (even non-editable by default) actually can be edited with a Right-Mouse-Click => Override.
MA Schedule B line 13b is calculated based on [Capital Gains/Losses Worksheet] lines 8 and 9. Line 8 have no Data Source, so I'm assuming this is the one which should be the original source of the data.
So put my Non-MA portion of short-term gains here, it was propagated to Schedule B line 13b and now my taxes are aligned my estimations.
