Look in your DCS installation ../Scripts/Database
In case of the Linebacker, look in the ../vehicles/SAM folder.
Open the M6 Linebacker.lua and find:
GT.Name = "M6 Linebacker";
Its the GT.Name entry you want to enter in CTLD the 'unit =' entry for all the units you want to add in CTLD. 'desc =' in CTLD is the name you see in the CTLD menu.
Some AA examples:
{ weight = 399, desc = "SA-19 Tunguska 2S6", unit = "2S6 Tunguska", side = 1, cratesRequired = 2 },
{ weight = 400, desc = "Strela 10M3", unit = "Strela-10M3", side = 1, cratesRequired = 1 },
{ weight = 401, desc = "SA-9 Strela-1", unit = "Strela-1 9P31", side = 1, cratesRequired = 1 },
{ weight = 402, desc = "M6 Linebacker", unit = "M6 Linebacker", side = 2, cratesRequired = 1 },
{ weight = 403, desc = "SA-8 OSA 9A33", unit = "Osa 9A33 ln", side = 1, cratesRequired = 2 },
{ weight = 404, desc = "Roland ADS", unit = "Roland ADS", side = 2, cratesRequired = 2 },
{ weight = 405, desc = "ZSU-23-4 Shilka", unit = "ZSU-23-4 Shilka", side = 1, cratesRequired = 1 },
{ weight = 406, desc = "M163 Vulcan", unit = "Vulcan", side = 2, cratesRequired = 1 },
Weight I think is just an ID, has to be unique for the given entry.