You can access the web view of the email if mirror page link is included in the email content https://experienceleague.adobe.com/en/docs/journey-optimizer/using/email/design-email/add-content/message-tracking#mirror-page 

Trying to understand the use case as to why multiple parallel wait activities are needed in parallel after a unitary event ? Are you trying to distribute the volumes over a period of time on the following lines ? Unitary events are anyways discrete. Reference - Limit throughput with External Data So...

You can take a look a this link https://support.google.com/mail/thread/49653586/list-unsubscribe-header-not-providing-the-option-to-unsubscribe?hl=en 

In the current state, there is no support to add fragments in landing pages as this shows up only in the code view. kindly log an enhancement request to adobe client care team.

In the current state, there is no support to add fragments in landing pages as this shows up only in the code view. kindly log an enhancement request to adobe client care team.

If the commerce.purchases event did not happen within the specified duration (timeout), it would traverse down the timeout path and we connect the Abandon message to this transition.If this event is recorded within the timeout duration, journey would end for the respective profile. So, no explicit f...

Read audience is for batch use cases and you can set the reading rate accordingly and further split the volumes using a combination of condition and wait activities to ensure the end point configured in custom action is not overwhelmed   Reference - https://experienceleague.adobe.com/en/docs/journey...

Throttling API will be needed to control the rate at which the downstream REST API's can process the requests initiated from AJOhttps://experienceleague.adobe.com/en/docs/journey-optimizer/using/configuration/configure-journeys/external-systems/throttling You can also take a look at this documentati...

Here is a reference document with details on how to pass arrays via custom actions.https://experienceleague.adobe.com/en/docs/journey-optimizer/using/orchestrate-journeys/journey-use-cases/technical-use-cases/collections If it is a array of simple data types, you can define it as a listString in the...

You can refer to this thread where a similar ask was posted https://experienceleaguecommunities.adobe.com/t5/adobe-campaign-standard/how-to-get-the-current-workflow-id/m-p/371281