Triggered by this I was hoping for an answer and got it now (please take a look of creation of post on TJC. No, not this forum! 
)
I am using now Fossify Contacts (earlier Contacts, but not working anymore) from F-Droid.
And I have my secondary address book!
Storing all relevant and for dark side accessible contacts (info) in another Android app, which manages Android contacts.
No need for another address book and struggling with WhatsApp not showing names.
After xx years there is still hope 