Solution
This is an expected result.
In the 19.1.0 release of the WLAN Toolkit, it installed a package called ni-wlan-toolkit-soft-front-panel. For the 23.5.0 release of ni-rfmx-waveform-creator, it installs a package called ni-rfmx-waveform-creator-wlan. Within that package's control file, it is configured to Provide the ni-wlan-toolkit-soft-front-panel package and it also conflicts with that same package.
Therefore, if you have WLAN Toolkit 19.1.0 installed and then try to install RFMX Waveform Creator 23.5.0 , NIPM will see that dependency and will need to remove the ni-wlan-toolkit-soft-front-panel package to allow installation of RFMX Waveform Creator. By removing ni-wlan-toolkit-soft-front-panel, NIPM will then also need to remove the WLAN Toolkit.