I don't have that cabinet, but have a couple of others that have a leaf spring that pops out from below the top piece when you lift the lid. One of mine needs to have the spring replaced I have to pull it out or push it in.
The part would look like
https://www.ebay.com/itm/1941-Singer...p2047675.l2557 or
https://www.ebay.com/itm/Vintage-Sin...IAAOSwgXZfYiY6 or
https://www.ebay.com/itm/Singer-Sewi...IAAOSwkoVeusuX
Unfortunately, the first one has ended.
Janey - Neat people never make the exciting discoveries I do.
Not affiliated with off-site link(s)