Hi @Vivek Agrawal ,
Thanks for letting us know your user experience. According to your case description, I do understand how frustrated you are now.
When I received the case, I searched a lot of documents did a lot of researches. I found this message means adding the app is supported in the SharePoint Store classic experience only. And I feel regretful to inform you that it turns out to be a by-design one.
And I noticed that some end users have also proposed the same request, it is highly recommended that you can vote this ticket. Many features of our current products are designed and upgraded based on customers’ feedback. With requirements like this increase, the problem may well be released in the future. Thanks for your understanding.
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