The idea of ADRs - architecture decision records - is that you capture any decisions that are made at the point at which they were made, with a little context about why. ADRs are often created in text or Markdown and checked into source control, so that they live with the code.
ADRs are, as they sound, not entirely about design, but about architectural decisions. Generally, the distinction is cost; if something will be very expensive to change at a later date, then it is probably architectural. Some decisions made during design sessions may be architectural in nature. Sometimes it is best not to worry too much about the distinction between design and architecture; recording the information is the most important part. Try creating an ADR if that is all that time allows.
ADRs are often only a few sentences. The content is more important than the formatting.