Hi again,
Actually, within the Main part of table node, grouping several rows under page-break protected folder works just fine... It is just that when one starts putting the page-break protected folders in Header part the things go awry. I don't believe the fix for that will be easy at all.
But since your HEADER_TABLE1 does not really need a header part to achieve same layout, I'd try as follows:
1) create page-break protected folder under Main part of HEADER_TABLE1; add an empty column of required width for %ROW2 and drag it under folder; create a new row type to hold %TEXT9 (just one column for the whole table width and no borders) and insert it before %ROW2; disable Header and Footer part for the table; re-position the table so its aligned to data table;
2) group the SAFETY_ITEM_ROW1 and MPO_DATA_ROW1 under page-break protected folder...
True, you'd have to add that empty column to the table. But that inconvenience pales in comparison with having to extricate the remaining height of Main window out of Composer innards via implicit enhancement, and the pain of having to calculate output height of dynamic layout elements in form itself and doing explicit page-breaks.
Just make sure to disable all (unnecessary) table headers and footers.
Attached form illustrates, and I've been unable to break the layout no matter what I tried 
. Or did you try the folders and did not succeed?
cheers
Jānis