l_simp_chinese:
pin_unpin_market:0 "关注市场"
pin_unpin_market_desc:0 "将其他[concept_country]的[concept_market]#header 钉选#!至概览窗口或从概览窗口#header 取消钉选#!"
pin_unpin_market_action_notification_name:0 "关注市场外交提示（请忽略）"
pin_unpin_market_action_notification_desc:0 "关注市场外交提示（请忽略）"
pin_unpin_market_action_name:0 "关注/取消关注[concept_market]"

Tried to find a way to dynamically determine whether the target country's market has been pinned, but it seems you can't access TARGET_COUNTRY or sth. similar in the context of diplo action description.

btw, I think you should provide localization files for each language. The content can be english text, but it at least avoids ugly code shown in the game.