gio:list-store-insert (store pos item)

store -- a g:list-store object
pos -- an unsigned integer with the position at which to insert the new item
item -- a g:object instance for the new item

Inserts the item into the list store at pos. The item must be of item-type type or derived from it. The pos argument must be smaller than the length of the list store, or equal to it to append.

Use the g:list-store-splice function to insert multiple items at the same time efficiently.