PSA: How to easily autofill using the new browser extension UI

The above PSA is intended to offer a constructive way to move forward for some fraction of users; I recognize that there may be reasons why some users do not wish to modify their current autofilling workflow. However, general complaints about the autofill functionality in the new UI should be posted in the feedback thread, not here. This thread is primarily for resolving any questions about the methods described above, or discussing the relative merits of these techniques, etc.