[missblit]

He's using the word as meaning "insert", not the JS function. He is saying he inserted a new row into a database to get admin access to a dashboard.

'splice" means to join two things as if by weaving them together. If used as "splice into" or "splice in" there is a sense of breaking something apart, inserting something into the gap, and joining it back together.

This all makes a bit more sense if you look up the etymology which was about ropes (despite splicing being about uniting, it's closely related to the word 'split').