Hi everyone,
We have an issue with something and I found what is causing the problem bu i don't know if the solution is actually possible.
Here's what's happened:
We have a custom entity called "Primary Case Email" which stores an email address of the custom open the case in CRM


When we click reply or reply all on a case email, we receive an error message, but if we click OK we can proceed with the reply, the only thing is that the email address from this file is getting neither in CC or TO.
We look further and found that actually, CRM cannot refer to it because cannot look into that entity at the first place.

We can see that if we start typing something in these two fields I can change to Accounts, Contacts, Users, and KB's (don't know who puts KB in To or CC but anyway)
The question is: How can I add a custom entity there as well, so that way the error might disappear because CRM will be able to look in Primary Case email entity and find the email address.
FYI: in classic interface, this entity is already available for search and the error doesn't occur when replying.

Please let me know if there's anything unclear.
Regards
Kiril