From what I’ve found there’s no default way to show a live updating status window during messages, so I built a small plugin for exactly this case. It’s a single .js file you drop into your project’s js/plugins folder and enable in the Plugin Manager. The filename needs to stay BazLiveStatusWindow.js since the plugin commands are tied to it.
For your poisoned character scene it would go like this. Plugin Command → ステータスウィンドウ表示 (Show Status Window), pick the actor, and optionally set 追加表示する変数 to a game variable like your trust value. Then Show Picture and Show Text as usual, the window sits in the top right during the conversation. When you use ステートの変更 to remove the poison or 変数の操作 to raise trust, the window updates that same instant, mid message. When the conversation ends, Plugin Command → ステータスウィンドウ非表示 (Hide Status Window).
The window shows the actor’s name, an HP gauge, state icons with names, and the optional variable line. Position and width are adjustable in the plugin parameters, and the shown state saves with the game. The plugin help is written in both English and Japanese so your editor will show whichever matches.