• I have tested the latest master version from http://builds.jabref.org/master/ and the problem persists

JabRef version 4.1 on Debian buster/sid

Steps to reproduce:

1. chain modifiers for the BibTeX key generator as described in the docs
2. have a BibTex file where both modifiers would have an effect
3. observe that only the last modifier will be applied

@Article{Interesting,
  title     = {The Interesting Title},
}

@Article{_interesting,
  title     = {The Interesting Title},
}

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