Hello Ivan,
Can't you just use the \column command of \markup to have two lines? Refer to the Notation Reference (NR).
Also, with respect, when asking for help on the list people usually provide an MWE, a minimum working example. For a case like this just a note or two would suffice. If you give an MWE it is a lot easier for people to help out, as they don't have to scan through large amounts of stuff that is irrelevant to the question in hand.