The next major release of CuteMarkEd will contain a tool to insert a table into the markdown document. 
This dialog makes it easy to define the size of the table, the alignments of the columns and the content of the cells. If the row or column count is changed then the table content part adapts to the change.
After clicking on the okay button, a markdown table is inserted at the current cursor position.
This feature was just merged and will be available with CuteMarkEd v0.8.0.