This pattern is not working 

<pattern>%d{HH:mm:ss.SSS} %-5level %logger{36} - %replace(%msg){'\n','\n'}%n</pattern>

This string "line a \n line b" becomes "line a n line b" (on the same line)

Workaround:

use regex capture pattern

<pattern>%d{HH:mm:ss.SSS} %-5level %logger{36} - %replace(%msg){'(\n)','$1'}%n</pattern>

This partially solve the problem because it is not possible to add different escaped char like a tab '\t'