Product mangers out there, how important it is to have a portfolio designed?

Never been asked for my portfolio ( SPM with 5 years of product experience)

I don't think anyone looks at these portfolios while hiring. The so called product communities like ProductFolks and the likes made it fashionable to have portfolios. It's not a differentiator. Almost every portfolio is a regurgitation of the same concepts that the courses offered by these community owners.

Important for folks making career switch to show understanding of concepts through portfolio I don't think experience folks require it but still I keep it visible in my resume

I have a portfolio for my entire work experience, nobody sees it. PM is a weird role like that . Very low trust. Almost as if everybody is making up stuff and putting it in a document. Unless an org is really desperate, they'll always ask for an assignment. It's good also in a way that they test your rigour fully . Also lots of times because of NDA's it's difficult to share stuff. So there's no right answer here. It's entirely upto you. If you think it can make your case stronger , make one and use it to take charge during interviews and anchor conversations.