...
You can add and edit annotations from the web or programmatically using the command line client, the Python client, the R client. Using the programmatic clients facilitates batching and automated population of annotations across many files. The web client can be used to bulk update many files using /wiki/spaces/DOCS/pages/2011070739.Adding and Editing Annotations via the Synapse UI
To add or modify annotations annotations on projects, files, folders, or tables in the web client, click the find the Tools menu in the upper right corner and select Annotations.
...
A new window will appear with a list of any previously added annotations. To add new annotations or edit existing annotations, click Edit.
...
In the pop-up window, add your annotations one at a time. Use the + icon to add multiple values for a single key and the x icon to remove values. Click Add New Key to add a new key.
...