Is it true with compound sentences one diagrammed on its own base line and the other compound sentence is placed on the dotted line that connects the verb?

Yes, in traditional diagramming of compound sentences, the main clauses are typically shown on their own baseline. The conjunction connecting the two clauses is placed on a dotted line that connects the verbs of each clause, illustrating the relationship between them. This visual representation helps clarify the structure and function of the compound sentence.