This appears a somewhat new behavior (perhaps introduced by new default settings in recent versions):
When I copy one bib entry from one bib file to another (standard CTRL+C in source bib file and CTRL+V in the destination bib file, the bib copied entry appears with a modified CitationEntryKey. Specifically, my citation entry keys are in general, all in the format:
_
The copied entry instead has a citation entry key in the format:
How can I avoid this behaviour and exactly copy of my bib entries “as they are” into the destination bib file?
I create document-specific BIB files from a master BIB file where I store all my bib entries, everytime I create a new project. Likewise, the project-specific BIB files also include new bib entries, that at the end of the project I want to transfer to the master BIB file.