We added the possibility to exclude certain file extensions in Release 22.214.171.1249. I think this can help you.
Windows GUI: SemanticSCM: Implemented a mechanism to disable Semantic Diff for certain file extensions. A semanticexcluded.conf file can be placed inside the Plastic SCM configuration directory: %HOMEPATH%/AppData/Local/plastic4. This file will contain patterns to match the files to diff. Semantic diff will be disabled for files whose path matches any of those patterns.
Example: Having the following semanticexcluded.conf file:
The semantic diff won't be displayed for the following items (server path format):
Anyway, we still have to remember last user preference (text diff / semantic diff). So, if the user changed it, it's remembered for the next execution. We will add this soon!
I will let you know when the preference is released.