This has been reported in another instance: it seems after the initial install, the Serial Input parameters are not set correctly in the Workflow tool, which is why the application is asking you to fill them in before saving your preferences.
Just put in some default values in there and the application will allow you to save all your preferences. This only needs to be done once as the Serial Input will from then on have its default values properly configured.
I hope this helps.
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Technical Product Manager
I don't want to achieve immortality through my work; I want to achieve immortality through not dying - Woody Allen