I wrote a pair of macros that employ @peternlewis' suggestion.
- One is a filter as he mentions above.
- Two is a macro that allows the user to activate macro one with a hotkey trigger.
Macro: Writing Keyboard Maestro Clipboard History Items to a File - #2 by ccstone
The hotkey trigger macro is a trifle slower than I like, because I have to resort to UI-Scripting with System Events – but it's not bad.
In any case it provides a smoother user experience than my first try.
Note – this method bypasses the [Close After Action] button setting of the Clipboard History Window. The window will always be left open, until the user elects to close it.