Hi @azadahmad thanks for getting in touch.
1. Can I add a slide that appears in all stories? I mean like adding ad unit of adsense shows ad in all story similarly tell any option by which add one slide then show in all story (for advertising purpose)
If you go to your Web Stories settings then you can select to use either Google AdSense or Ad Manager from the Monetization section. You can find more information on advertising in Web Stories here.
2. I have a subdomain website whose stories are not getting indexed. Are there any separate guidelines for subdomain website.
This isn’t something that is controlled by the Web Stories plugin itself, but we’re working with the Search Console team to see if anything has changed on their end recently that could be causing any indexing issues.
It is worth noting that there are a number of factors as to why this might be happening and if you haven’t already I would recommend checking the Search Console Help Center which may help you to find out why this may be happening.
Hope this helps to answer your questions but let me know if you have any further questions.
