My understanding of inference:

“One draws inferences from the individual propositions and thus connects the individual propositions. That is like reading between the lines and that helps filling the gaps.”

Yes—for the kind of historical inference we have been discussing, that is a useful formulation.

For example:

Statement A:

Slavery was abolished.

Statement B:

Industrial employers required workers.

You may infer:

Formerly enslaved people could now potentially enter wage employment.

The inference connects A and B and fills a conceptual gap that is not explicitly stated in either sentence.

One caution: “reading between the lines” can mean either legitimate inference or unsupported speculation. The inference must still be defensible.