Right now, seems like even if I want to add log files to be monitored, it would have a logs written by some processes? (which is why I can only configure log in 'process' page, not 'host' page?)
Say, for example, if I want monitor a log which the is /var/log/abcd.txt. How can I achieve this?
You can define a custom log event on a log file on a host in the Log Analytics settings. This would allow Dynatrace to alert on certain log patterns that you define that it may find in that log file.
Woops, you are right. Here is information on how to manually specficy a log file to be captured.