Alexa Skills Dialog Management: how to repeat last intent without specifing its utterances again

You're on the right track. The thing to remember is you can have one intent for multiple slots and NOT require them all.

Here's how you can create a single intent for all of it.

The sample utterances are:

How are things on the {floor}
And on the {floor}
What is the {condition}
What is the {condition} on the {floor}

Then you create the "condition" and "floor" slot types, filling them with appropriate sample values like "temperature" for condition and "first floor" for floor. Then make sure to assign those slot types to the slots in your intent.

Then your handler code looks like this...

    const conditionIntentHandler = {
      canHandle(handlerInput) {
            return Alexa.getRequestType(handlerInput.requestEnvelope) === 'IntentRequest'
                && Alexa.getIntentName(handlerInput.requestEnvelope) === 'conditionIntent';
        },
        handle(handlerInput) {
          var speakOutput = "";
          var condition = "";
          var floor = "";
          const attributesManager = handlerInput.attributesManager;
          const attributes = attributesManager.getSessionAttributes();
          
          if (handlerInput.requestEnvelope.request.intent.slots.condition.hasOwnProperty('value')) {
            condition = handlerInput.requestEnvelope.request.intent.slots.condition.value;
          } else if (attributes.hasOwnProperty('condition')) {
            if(attributes.condition !== "") condition = attributes.condition;
          }    
            
          if (handlerInput.requestEnvelope.request.intent.slots.floor.hasOwnProperty('value')) {
            floor = handlerInput.requestEnvelope.request.intent.slots.floor.value;
          } else if (attributes.hasOwnProperty('floor')) {
            if(attributes.floor !== "") floor = attributes.floor;
          }    
        
          if (floor !== "" && condition === ""){
              speakOutput = "Here's the conditions for the " + floor; 
          }  else if (floor === "" && condition !== ""){
              speakOutput = "Here's the " + condition + " throughout the house";
          } else if (floor !== "" && condition !== ""){
              speakOutput = "Here's the " + condition + " on the " + floor;
          } else {
              speakOutput = "I have no idea what you're saying. Are you okay?"
          }

          attributes.floor = floor;
          attributes.condition = condition;
          attributesManager.setSessionAttributes(attributes);
          
            return handlerInput.responseBuilder
                .speak(speakOutput)
                .reprompt('What else can I tell you?')
                .getResponse();
        }
    };

I haven't written the actual code to present the values, just placeholder responses, but you should get the idea. Add more carrier phrases that contain one or both slot types to make this handle more ways people might ask for this info.