After using and considering this for a while, I've decided that I like my alternative 2:

'An alternative choice would be to create a 3d prefix option, a new sibling to SuffixPattern and StackTracePattern. Might put to much of a burden on the casual user to understand yet another option, so I didn't do this'

a lot better than my third option, which I implemented in my original pull request:
'My third option, (which I implemented) was to recycle the StackTracePrefix for these special loglines. This turns out OK (see log example below), but doesn't allow me to make these special log lines stand out (by using a reduced indent). Standing out is kind of the purpose of these special lines, they're used as separators/headers for stacktraces.'

Will be updating the pull request once it has been tested a bit.
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