After updating version 2.11.0, we found thatNMSManager.getProvider ()'s opentradewindow (tradeui, recipes, player)method has been abandoned. I need him very much. Is there a new alternative?
Thank you very much.

This method has already been removed during the update to MC 1.13. It is now possible to setup and open custom merchant inventories via the Bukkit API. See https://hub.spigotmc.org/javadocs/spigot/org/bukkit/Server.html#createMerchant(java.lang.String)