Learn Danish: En viking kan have tabt mønten her. - A Viking may have dropped the coin here.

This is the core of epistemic speculation. By combining the present tense modal kan with the perfect infinitive have tabt, you are expressing a present guess about a past event. It translates directly to "may have dropped," showing that you currently think it's a possibility that this happened in the past.

Why is the word for "dropped" tabt? Doesn't Danish have the word droppet?

Yes, but they mean different things. At tabe (past participle tabt) means to drop something accidentally or to lose it, which fits a dropped coin. At droppe is used for dropping a class, abandoning a plan, or dumping a boyfriend/girlfriend.

If I want to add the adverb måske (maybe) to emphasize the speculation, where does it go in this long verb chain?

Central adverbs like måske go immediately after the first finite (conjugated) verb in a main clause. So it would slide right in after the modal: En viking kan måske have tabt mønten her.

Will a Dane actually enunciate all three verbs kan have tabt clearly?

Rarely! In everyday speech, the auxiliary verb have in these modal constructions gets heavily reduced. Instead of a full have, you will often just hear a short "a" sound, making the phrase sound like kan-a tabt.