New in Google Slides

Insert slides from Google Slides into Google Docs

You can now insert a slide from a Google Slides presentation directly into Google Docs. If you want, you can then link that slide in Docs to its source presentation in Slides and sync any changes with just one click, similar to the way you can insert and link charts from Google Sheets.
How to insert and link slides in Docs.

Guides and rulers

You can now add guide lines for consistent placement and alignment throughout a presentation. These guides will show on all slides in a presentation, and text and objects will snap to a guide to ensure they’re aligned.

Google has also added a new visual ruler that gives you fine-grained control over the alignment of text, lists, objects, and guides. Indentation markers in the ruler can help you control the alignment of text or bullets within objects. How to use guides and rulers in Slides

Comment on text within individual objects

You can now comment on specific text within an object, such as a text box, on a slide.