Add code snippe below to your grid:
plugins: [{
ptype: 'rowexpander',
rowBodyTpl : [
'<p>{yourcolumn}</p>'
]
}],
How to expand all after store finishes loading?
I got many answers from google but they did not work!
Do not use
expander.expandRow(rownum);
Instead you should use
expander.toggleRow(rownum);