How to access elements from settings.xml in pom.xml with Maven?

According to https://maven.apache.org/pom.html#properties it should be possible to use ${settings.x} to access the element <settings><x>value</x></settings> from the settings.xml file in the pom.xml file.

However, when I try something like

  <profiles>
    <profile>
      <activation>
        <file>
          <exists>${settings.localRepository}/path/to/file</exists>
        </file>
      </activation>
    </profile>
  </profiles>

in my pom.xml it isn't replaced in the effective pom.xml. When I replace ${settings.localRepository} with ${user.home}/.m2/repository it works fine but that's not what I want. Is there anything I can do to fix that? (Tested with Apache Maven 3.6.0.)

Background information: I have a dependency that isn't present in an online maven repository and I can't change that. It must be compiled by users and can be installed to the local repository. Instead of doing this manually, I'm trying to do this automatically in my pom.xml. For this I have to ignore the dependency if it's not present in the local repository. Hence the profile that checks if the file is present in the local repository. Without the profile, maven wouldn't even start the life cycle because the dependency can't be resolved. Of course the project won't compile the first time the pom.xml is executed. But all dependencies are automatically installed and the project will compile in a second pass. I know that this isn't a clean solution but I think it's better than telling users to compile and install dependency xy manually before this project can be compiled. I also include a build script that first runs mvn clean initialize to install the dependencies and then mvn clean compile.

Put the source of the external dependency in an own project like:

+- main
   +- pom.xml ... <packaging>pom...<module>external...<module>internal
   |
   +- external
   |  +- ... Maven dirs as usual ...
   |  + pom.xml
   |
   +- internal
      +- ... Maven dirs as usual ...
      +- pom.xml ... <dependency>external

Such when building main the Maven Reactor takes care of the projects' build order (build external first, then internal in this case) and you can forget about dealing with settings.xml, repositories, profiles or properties.