Suggestions? iMessage combines texts from same contact with multiple numbers into one message making it near impossible to choose which phone to text

This feature has been on iMessage on MacOS for a while. If you have a contact with multiple phone numbers (iPhone or not), iOS now combines messages from both numbers into one thread. The issue I have is if I've been chatting with my contact with Phone Number 1 then want to convert to Phone Number 2 (assuming both are iPhones, these would be different Apple IDs though the same contact in my address book, but it's not always that they're both iPhones), when I do a search for that person's name, the only number available is Phone Number 1, seemingly because it's recognizing that as the one that matters. I have to actually type in the phone number. If the contact contacts me with Phone Number 2, that is now set as the 'live' number. I don't seem to have any control on iOS like I used to on MacOS (Catalina seems to have removed this feature, but that's a matter for a different post), which lets you click the name of the contact and get a list of numbers in a drop-down to force which number is chosen. Any recommendations on how to deal with this? I have a number of contacts who have multiple phones for work and don't necessarily have both phones on them at the same time. I can't seem to figure out how to select the number I want on iOS without memorizing all the numbers.