I am sorry for the delayed response, since I am awaiting for the response from our development team.
I have discussed the matter with our development team. Actually, the "Tool Tip" property for PPT Hyperlink is unavailable. The second option for embedding an invisible image with alt text is available in Aspose.Slides for .NET. The alt text property can be set by using Shape.AlternativeText property and invisible shapes can be created by filling shape with transparent color using Shape.FillFormat.Transparency property. Unfortunately, the animations does not provide hover text feature. Please feel free to share, if you have any further inquiries.
Thanks and Regards,