With permission, you can create and set size options for assets shared through share links, embed codes, and embed links. These will be available for all DAM users who have permission to select.
To set this up, go to the Admin app, select Order Settings and Share links. On this page, you can create, reorder, and delete pre-determined sizes. You can also decide where in the DAM you want the sizes to show up. Note that turning on Search & Details allows the size to show up in search results, Asset Details and Digest, and Quick View.
In the updated share experience, these pre-determined sizes can be selected for embed codes and links only. In the legacy experience, you can select a pre-determined size for share links too.