Threads and merging records in Contact by Zaweba
The Threads strip in Contact by Zaweba groups a record's emails by reply and subject, and Merge records folds a duplicate into the right one with an Undo.

A good customer writes to you about lots of things. There is the original order, a question about delivery, a quote for something new and, now and then, a complaint. Contact by Zaweba keeps all of that in one conversation per record, which is the point of the app, but one conversation does not have to mean one long jumble. The Threads strip sorts the emails into their separate strands, and Merge records deals with the opposite problem, when one customer has ended up split across two records.
The Threads strip
Inside each record sits a Threads strip that groups the emails by their replies and their subject. A reply chain about an order becomes one thread, a separate chain about a quote becomes another. Click a thread to see just its emails, which is a quick way to pick up a matter where you left off without scrolling past everything else the customer has sent.
Right-click a thread for the things you can do with it. You can rename it, which helps when a customer's subject line is something unhelpful like Re: Re: Fwd: hello. Calling it Kitchen quote or Missing parcel makes it findable months later. You can mark the whole thread read or unread in one go, and you can mute it, so a long chain you don't need to watch stops demanding attention.
Moving and merging threads
Sometimes a thread belongs somewhere else. A customer might start writing about a second business they run, or forward something that is really a new enquiry from a friend. Right-click the thread and move it, with its future replies, to another record, or to a brand new enquiry or customer. The future replies part matters: when the next email in that chain arrives, it follows the thread to its new home rather than landing back where it started.
Threads can also be merged, for when the same matter has been split by a customer changing the subject line halfway through. Merging them puts the story back together in one strand.
Merge records for duplicates
Duplicate records creep in. Someone enquires through your website form and again from their work address, or two people at the same firm write in before you realise they are colleagues. You end up with two records for what is really one customer.
Merge records folds one record into another. The emails and history come across so you have a single conversation again. Like other changes in Contact, the merge is listed in Recent actions with its own Undo, so if you merge the wrong pair you can put them back.
Before merging, it is worth deciding which record should survive. Usually that is the older one, or the one already converted to a customer, so its place in your customer folders stays as it is.
Good habits with threads and merges
Rename threads early, while you remember what they are about. A clear name costs five seconds and saves a lot of scrolling later.
Mute rather than ignore. A muted thread is a decision you have made; an ignored one keeps showing as unread and makes the record look busier than it is.
Move a thread rather than a single email when a whole matter belongs elsewhere. Moving one email fixes today but leaves the next reply to land in the wrong place. If only one email is out of place, the Why is this here? command on that email explains how it got there and offers the right fix.
Merge when it is clearly the same customer, not just the same company. Two separate departments of a big organisation may be better kept as two records, with domain matching thought through on each, so neither conversation fills up with the other's mail.
How threads fit the rest of the app
Threads live inside the conversation view, alongside the sender chips that filter to one person and the cards with Reply and other actions. Status still works across the whole record, so muting a thread does not hide a customer who is waiting for an answer elsewhere in the conversation. The result is one record per customer, readable a strand at a time, which is about as tidy as a busy customer's history gets.