What tense is always used to indicate a connection between actions that happened in the past?
I think the answer to the question given is "there isn't simply one way to indicate a connection between actions in the past". See below for examples.
I think the question being asked is to identify the tense that allows for relating actions in the past and perhaps giving them a sense of order (for example, Action A occurred in the past, Action B occurred before Action A, etc). In practice, a sentence of that sort could look like:
Andrew ate dinner after he did his homework.
This uses simple past tense twice with the word "after" giving a sense of order to the timing of each action. This sentence gives indication that the "narrator" is in the present and is giving an account of what Andrew did in the past.
I could also write:
Andrew had planned to eat dinner after he finished his homework, but instead simply went to bed.
This uses past perfect simple tense to order eating and homework. Again, the "narrator" sits in the present but this time tries to show the mindset of Andrew at the time he was doing his homework.
Andrew was eating dinner when he realized he hadn't finished his homework.
This uses the past progressive tense by the "narrator" to firmly place the reader with Andrew in his eating of dinner (which is in the past, as indicated by the past part of the tense) as he realizes he hasn't finished something that should have been done in the past (and that tense is past perfect simple again).
And so I think the answer to the question given is "there isn't simply one way to indicate a connection between actions in the past".