More information needed
The TT$_, tt2$_, and TT3$_ are defined in starlet and adding new
bits is non-trivial. There is little reason why they should need to
add or redefine any of them. They do need to get them correctly set
for what they are doing. It is hard to tell them what setting they
need.
Although it might not provide a solution in this particular
case, then general method for defining terminal capabilities
on VMS is through SMG using editting SYS$SYSTEM:SMGTERMS.TXT
and compiling that with SYS$SYSTEM:SMGBLDTRM.EXE to build
a new TERMTABLE.EXE. This process is documented in chapter 5
of the OpenVMS RTL Screen Management (SMG$) Manual.