We have a problem where someone wants to use a skill as a command, but the command should not appear unless certain conditions are met.

By default, the "use_skill" command will simply disable the command if it cannot be used.

There are several solutions. Personally I would prefer to simply define a custom command type, even if it will only be used once.

I use the standard command plugin API to define my command, except because I know it will function the same way as the use_skill command, I can basically have this command invoke the other command.

In this case, I want to define a command that will be hidden if it's not usable:

CommandManager.register(:hide_use_skill, :actor, "1.0")

class Command_HideUseSkill < Game_BattlerCommand
  def enabled?(user)
    user.usable?($data_skills[@ext])
  end
end

class Game_Actor < Game_Battler
  def add_command_hide_use_skill(args)
    id = args[0].to_i
    name = $data_skills[id].name
    cmd = Command_HideUseSkill.new(name, :use_skill, id)
    add_command(cmd)
  end
end

Now instead of saying

<cmd: use_skill 43>

I can instead say

<cmd: hide_use_skill 43>

And it will do basically the same thing except it will not be visible if it can't be used.