Note that SCS has tra files in several places. Most of them are in stratagems\lang and stratagems\lang_som, but there is also two in stratagems\sfo2e\lua\lang and one in stratagems\iwdspells\lang.

Translating SCS item description files

An item description, in SCS's tra files, consists of three blocks:

(1) the description of the item, along with its statistics
(2) a unique string, which in English is either 'Usable by:' or 'Unusable by:'
(3) a list of who can or can't use the item

If SCS is installed on an Enhanced-Edition game, blocks (2) and (3) are stripped out, because the engine generates them automatically.

To make sure this works in your language, you just need to make sure that the unique strings, which occur at @100400 and @100401 in shared.tra, occur *exactly as written* in your item descriptions. SCS uses the strings in shared.tra to work out what to delete from your item descriptions.

(Matching the way these strings appear in the actual game is unnecessary: all that matters is that the shared.tra lines match what's in your item description translations.)