Version: 7.0.1.2 (x64)
OS: Windows 10
A spreadsheet cell grid is rigidly locked to the row/column coordinates. You can merge a rectangular region of cells to appear as one larger cell, but you cannot have additional cell borders between the row/column borders. this is different from the structure of insertable tables (in e.g. Writer), where you can split and merge cells horizontally and vertically at will (albeit to a limited degree of complexity).
Composite cell content can be split, and distributed to multiple cells as per @igorlius’ answer. A single cell cannot be split, except for the restoration of merged blocks. To split a previously merged block, select the merged cell, and then click the Merge tool or one of the menu items in Format - Merge cells
Hello,
if the text content you want to seperate (has a common delimiter eg. comma, semicolon) you can use
Data → Text to Columns to split the cell
Hope that helps.