Merge multiple matrix questions into one for ongoing survey

We have an ongoing survey that has had many changes over the years. There are 2 matrix tables and both have the majority of their statements now hidden from respondents, but we keep the old statements in the survey to retain the historical data. To improve survey design we want to combine the statements that are still shown to respondents so they are in one matrix table. I am wondering what the most efficient way to migrate these statements would be. We need to add the statements and also move the historical data into the new field because it will be trended on the dashboard.
What I am thinking right now: add the statements from 1 table into the other as new fields and then manually move the data from those statements to the new fields. I would filter the data by scale point -> select all responses -> add that scale point into the new field -> repeat for each scale point (9 point scale) -> delete the old statement from the matrix
Not too difficult but manual and annoying. Are there any simpler or more efficient ways to do this?