Every feature within the release can have its own milestones which cannot accurately be represented through requirements. Basically think of requirements stemming from the milestones for a particular feature. Would love to have that functionality in Aha! instead of maintaining a timeline in a separate tool.
|Release time frame|
This can be achieved today through the use of custom fields. You could create a Milestone by using a "date" custom field at the Feature level. This could then used on your timelines.
Here's more background on how to add and use custom fields: https://support.aha.io/hc/en-us/articles/202000937-Add-custom-fields-across-Aha-