The specific sequence you inquired about, from * to **, does not involve any microtasks being performed immediately. However, a microtask is scheduled for later execution during this sequence.
When an async function is called, it behaves synchronously until encountering the first await, uncaught exception, or return statement. At that point, a promise is returned and the synchronous execution resumes from the caller's context. If there was an exception or a return, a microtask is queued to handle the promise resolution (either rejection or fulfillment).
The parts of the code that are synchronous have been highlighted in yellow:
https://i.sstatic.net/zRDN7.png
In your scenario, when you invoke async1 at the end, its synchronous part runs by logging Async 1, then calls async2 which logs FROM async 2 synchronously. Upon receiving a promise from async2, async1 encounters the await keyword and returns its own promise. Subsequently, synchronous execution proceeds after this call, logging Synchronous.
Between the segments marked with * and **, a microtask is queued to handle the completion of the promise from async2. Once the current task completes, this microtask is executed, resolving async1's promise. Following this, async1 continues its operations, performs the log, and implicitly returns. A final microtask is queued to process this last settlement, but since nothing depends on this promise at that stage, no visible outcome occurs.