Show child table popup to create/edit by javascript

For limitation of 10 columns in child table, (Which I want to show 15 colunns as my bussiness reqs),
I already added a custom table (using Handsontable js) to load child table data.
The data load successfully.

Now want to show Child table Popup to Create/Edit a child table item by calling javascript.
How can I do this, please.