Learn Swedish: Skådespelaren stod på scenen med manuset i handen. - The actor stood on the stage with the script in his hand.

When using this med construction to describe how someone is holding their body or personal items, Swedish prefers the definite form (handen) over a possessive pronoun (sin hand). Because the context makes it completely clear whose hand it is, the possessive pronoun is considered redundant.

How does the descriptive structure med manuset i handen function in this sentence?

This is a classic absolute construction used to set a scene. You take med (with), add a noun phrase (manuset), and follow it with a location or direction (i handen). It describes the physical state or posture of the actor while the main action (stod på scenen) was happening.

Is manuset an en-word or an ett-word, and what is its base form?

It is an ett-word: ett manus (a script). To make it definite, you add the suffix -et to get manuset. It is a very common abbreviation of the longer word ett manuskript, which works the exact same way.

Could I use i scenen instead of på scenen?