SiftingAppender with no Default value discriminator

I use SiftingAppender and RollingFileAppender to separate log folders with a discriminator key.

<appender name="TEST_LOGGER" class="ch.qos.logback.classic.sift.SiftingAppender">
  <discriminator>
    <key>discKey</key>
    <defaultValue>Default</defaultValue>
  </discriminator>
  <sift>
...
  </sift>
</appender>

But I just need the discriminator keys that set and don't need a folder with name of defaultValue. is there any way to just separate needed folders and remove others?

After a lot of searching in Logback docs, I found that by using the filtering method, it is possible to register the required values and not register the other values.

<appender name="TEST_LOGGER" class="ch.qos.logback.classic.sift.SiftingAppender">
   <discriminator>
     <key>discKey</key>
     <defaultValue>Default</defaultValue>
   </discriminator>

  <filter class="ch.qos.logback.core.filter.EvaluatorFilter">
   <evaluator class="ch.qos.logback.classic.boolex.JaninoEventEvaluator">
      <expression>
        mdc.get("discKey") == null
      </expression>
   </evaluator>
     <OnMismatch>NEUTRAL</OnMismatch>
     <OnMatch>DENY</OnMatch>
  </filter>

  <sift>
  ...
  </sift>
</appender>

Above code do not register Default folder.