Assign a custom field to several profile groups

Assign a custom field to several profile groups

context : I have several profile groups and for some of them, i want to add the same custom field. As it is not possible for now, i have to create a similar custom field for all the profile groups i want. Then, i create a new similar category custom field assigned to each corresponding profile group and i set the default value corresponding to the profile group custom field. That is convenient because when a user adds a new ad, this field is already filled (gain of time).

The big issue is : as there are several category custom fields, i can't make a unique global search filter for those similar fields (that contain the same kind of information) !! I should display as many search fields as they are similar custom fields, that doesn't make any sense because there will be several same-looking search fields with the same options ! 
I hoped conditional fields could solve that but no.

Thus, the only way i see is to add the possibility to set several field groups to a custom field.
Thus, for instance, i will create a custom field specifically for group B and group C. Then i will create a unique category custom field that i will "link" with this previous unique profile custom field. With that, i can activate the search feature and there will be only 1 search field !

Is that clear enough for you ?
It's a small improvment but a big admin and user UI/UX improvment !

What do you think about that point ?
Eager to looking to your comment,
Best !