How exactly are you specifying multi-line texts? This is something ZDoom never supported so I have to see a properly defined file in order to support it.
This is something supported by Zdoom, and since a long time!!!
You have only to put multi-lines in your dehacked patch, and to count properly. That's it !!!
I made this discovery by accident some years ago...
As example, here is a dehacked patch that I made for
Mortiser, Doom II pwad made by Sam 'Metabolist' Woodman (2000-2003).
[spoiler]Patch File for DeHackEd v3.0
# Level names & text fix to *Mortiser* in Doom Legacy.
# Author : Jean-Yves Delpech aka "Jive", 51
# Email Address :
dlw@doomwadstation.com
# Web site :
http://doomwadstation.com/dlw/
#
# type "Legacy -iwad doom2.wad -opengl -file Mortiser" to run.
#
# If you don't have Doom Legacy yet, you'd better get it immediately
# Original game & sources by: Id Software.
# Additions (c)1998-01 by: Fabrice Denis & Boris Pereira
# OpenGL version (c)1999-2005 by: Thierry Van Elsuwé
# Web site:
http://student.ulb.ac.be/~tvelsuwe/DooMlgl/DooMlgle.htm
# e-mail:
hurdler@newdoom.com (Thierry Van Elsuwe)
#
bpereira@newdoom.com (Boris Pereira)
# Web site:
http://legacy.newdoom.com/
# e-mail:
legacy@newdoom.com
#
# Special thanks to Steven McGranahan, Robert Bäuml and Bell Kin for
# their large contribution and to others Legacy Team members.
#
Doom version = 19
Patch format = 6
Text 17 58
level 1: entrywayLevel 1: Lookout Base
Music: *Rage* by Mark Klem /REQMK01/
Text 19 68
level 2: underhallsLevel 2: Ice Station Alpha
*Damage Assessment* by Mark Klem /MM2MK13
Text 20 95
level 3: the gantletLevel 3: Supply / Shipping Depot
Music: *Dance of the Sugarplum Lunatic*
by Mark Klem /MM2MK30/
Text 18 62
level 4: the focusLevel 4: Chemical Plant
Music: *Dredge* by Mark Klem /MM2MK21/
Text 26 58
level 5: the waste tunnelsLevel 5: Toxic Waste Dump
Music: *Grave Town* by Mark Klem
Text 20 31
level 6: the crusherLevel 6: You're back to Doom II
Doom *Mortiser* Level-names & Text fix by Jive for Doom Legacy 1.42[/spoiler]
For the fact to put one line upper the beginning of the description under the automap, do you think that it could be possible to implement it?
At least, under Legacy, with the transparency feature, I don't have any problem.
The display of "Mapxx" is unuseful. Too bad to see it twice on the screen:
"Map06: Level 06: You're back to Doom II"
Anyway: I propose, you decide!

Thank you!