You are right, pull-to-refresh was not very discoverable ;) Somehow I an auto-update function for a tab called "history".
Another thing I just realised is the number of new devices in the notification label. Let's say I put ramble in the background. After 10 minutes it tells me that there are n_1 new devices. I click on the notification in order to check them out. If I then put ramble in the background and it finds n_2 new devices then the notification says that there are now n_1 + n_2 new devices. I would expect that it says n_2 devices.
The notification is a summary of the current scan (until you stop it). New devices are ones you've never seen before the current scan. I often run it on my commute, the 'total' number give me an idea of how busy (in terms of BLE devices) it is today.
Another thing I just realised is the number of new devices in the notification label. Let's say I put ramble in the background. After 10 minutes it tells me that there are n_1 new devices. I click on the notification in order to check them out. If I then put ramble in the background and it finds n_2 new devices then the notification says that there are now n_1 + n_2 new devices. I would expect that it says n_2 devices.