Can we create a Combobox for custom activity

LocalizedEnum is the method form UiPath.Shared project.
add this import in file where you have InitializeComponent method:

using UiPath.Shared.Activities.Localization;

KsefEnviroment is our custom enum. We defined it in UiPath.Shared.Activities.Localization namespace to have direct access:

namespace UiPath.Shared.Activities.Localization
{
    public enum  Environments
    {
        [LocalizedDescription("TEST")]
        TEST,
        [LocalizedDescription("DEMO")]
        DEMO,
        [LocalizedDescription("PROD")]
        PROD
    }
}

This enum is used in .Activities project in activity code:

[LocalizedDisplayName(nameof(Resources.InitSessionByToken_Environment_DisplayName))]
[LocalizedDescription(nameof(Resources.InitSessionByToken_Environment_Description))]
[LocalizedCategory(nameof(Resources.Input_Category))]
public Environments KsefEnvironment { get; set; }