In order to create a table as shown below, I have drawn a white rectangle and for the "grid lines" I have drawn several narrow rectangles. I then used Path -> Difference to "cut" the lines out of the rectangle, resulting in transparent grid lines.

Now I want to modify the table, increase the row height of one row, to allow for two lines of text.
So I want to "undo" the Path -> Difference, to get my white rectangle and the other "grid line" rectangles back, move some rectangles and apply the Path -> Difference again. Unfortunately, that appears not to be possible. (I can use the inkscape undo function right after applying the difference, but that's not what I mean, I want to save the file, open it again a day later and then undo the "difference" operation).
The final table will have two columns and 30 or more rows, with various heights, and several rows that have multi column span, which must be relatively easily maintainable afterwards. Initially I looked at many small white rectangles with text captions on them and arrange these in rows and columns. As my table was growing, that became worse and worse maintainable, so that's not the direction I want to go and now I'm looking for a better way.
I've been messing around with clipping and masking to achieve what I want, but up to now, failed miserably.
Any help is highly appreciated, thanks in advance.