ClientMods/CustomInteractions/Plugin.cs

using Aki.Reflection.Patching;
using BepInEx;
using EFT.UI;
using System.Linq;
using System.Reflection;

using DynamicInteraction = GClass2900;
using ItemContext = GClass2710;
using ItemInfoInteractions = GClass2901<EFT.InventoryLogic.EItemInfoButton>;

namespace IcyClawz.CustomInteractions
{
    [BepInPlugin("com.IcyClawz.CustomInteractions", "IcyClawz.CustomInteractions", "1.2.0")]
    public class Plugin : BaseUnityPlugin
    {
        private void Awake()
        {
            new ItemUiContextPatch().Enable();
            new InteractionButtonsContainerPatch().Enable();
        }
    }

    internal class ItemUiContextPatch : ModulePatch
    {
        protected override MethodBase GetTargetMethod() =>
            typeof(ItemUiContext).GetMethod("GetItemContextInteractions", BindingFlags.Public | BindingFlags.Instance);

        [PatchPostfix]
        private static void Postfix(ref ItemInfoInteractions __result, ItemUiContext __instance, ItemContext itemContext)
        {
            foreach (var provider in CustomInteractionsManager.Providers.OfType<IItemCustomInteractionsProvider>())
            {
                var customInteractions = provider.GetCustomInteractions(__instance, itemContext.ViewType, itemContext.Item);
                if (customInteractions != null)
                {
                    foreach (CustomInteraction customInteraction in customInteractions)
                    {
                        __result.AddCustomInteraction(customInteraction);
                    }
                }
            }
        }
    }

    internal class InteractionButtonsContainerPatch : ModulePatch
    {
        protected override MethodBase GetTargetMethod() =>
            typeof(InteractionButtonsContainer).GetMethod("method_3", BindingFlags.NonPublic | BindingFlags.Instance);

        [PatchPrefix]
        private static bool Prefix(ref InteractionButtonsContainer __instance, DynamicInteraction interaction)
        {
            if (interaction is CustomInteractionImpl customInteractionImpl)
            {
                __instance.AddCustomButton(customInteractionImpl);
                return false;
            }
            return true;
        }
    }
}