so I found I could put it in landscape mode
I understand this as insertion of a landscape page in the middle of a sequence of portrait pages. You then inserted the table in this landscape page. The fact that the page is landscape or portrait does not come into account for splitting.
how to split the table across two sheets
This expression is ambiguous: a table can be split horizontally producing two tables one above the other, or vertically resulting in two tables side by side.
##“Horizontal” split
Put the cursor in any cell of the row which will become the first row of the second table and Table>Split Table. You can choose whether or not you copy the eventual heading row into the second table.
##“Vertical” split
This is not possible because a table extends from its left limit to its right limit.
To make such a vertical split, you must first create another table somewhere below the present one, copy the right part content into the new table and delete the copied part (leaving only the left part). The remaining “half” of the original table will be redistributed across the full width of the page (unless you manually configure it otherwise).
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