I think I have worked it out for myself. The documentation says that PMs Edit-Search is based on the Spotlight feature in MacOS. So the available search fields are probably determined by Spotlight.
Spotlight has very powerful search facilities when used via the Finder (Finder-File-Find). The default drop-down menu Kind offers only a small subset of all the metadata that is available to be searched. As well as general file-related items, there are also these for images:
acquisitionMake, acquisitionModel, aperture, bitsPerSample, cameraOwner, colorSpace, exifgpsVersion, exifVersion, exposureMode, exposureProgram, exposureTime, exposureTimeString, flashOn, fNumber, focalLength, focalLength35mm, hasAlphaChannel, isoSpeed, layerNames, lensModel, maxAperture, meteringMode, orientation, pixelCount, pixelHeight, pixelWidth, profileName, redEyeOn, resolutionHeightDPI, resolutionWidthDPI, whiteBalance.
These are the technical names, PM and Spotlight present them in a more friendly fashion.
To find them, and add them into the Kind-list, select Other at the bottom of the Kind drop-down menu. Detailed AND/OR queries can then be constructed and Saved, similar to Smart Folder facilities. Results could go into a folder for examination by PM.