I have two exec nodes. I would like the second one to start after the first one finishes successfully. How to connect them? Should I just connect output of the first one with the input of the second one? If that is the case, which output of the first one should I choose, since there are three?
Welcome to the forum @Demokedes8
That depends on how the first exec node is configured. Have a look at the help text for the exec node, understand what each output contains, and decide which one you should use. Note that if you have selected the output "While the command is running" then there may be multiple messages coming from output 1. Also you might want to check the return code when the first one has completed in order to check that it ran successfully before running the second command.
Finally, you might like to consider using just one node running multiple commands in series. For example, on a Linux system you can use
cd /some/path && command1 && command2
or you could write a shell script to execute the commands and run that.
Out of curiosity, what are the commands doing that need them to be ran after one another?