html – redirects a blog to another (Blogger)

I have a blogger blog with his own domain (I'll call him www.mywebsite.com) that is to say: this site was a www.mywebsite.blogspot.com and I bought a domain name later; I can continue to manage settings from the Blogger control panel.

Now, another webmaster will write my name on a page of his website and I would like it to insert a hyperlink to allow users to be redirected to mine (when they click on my name).
BUT I do not want to provide the URL of my website because I would like to stop redirection immediately if I change my mind (in case I do not want my website to be associated with others).

That's the reason I created another blogger blog (I'll call it www.bloggerblog2.blogspot.com) and I try to use this new address to redirect to www.mywebsite.com.
I can not do it from Blogger settings because an error message is displayed. More specifically, I'm on Settings -> Search preferences -> Custom redirects -> New redirects. At this point, I write both URLs and save them but I get the error message

Source and destination values ​​can not be empty or more than 256
characters and must begin with /.

I wonder why am I getting this error?
Can I handle this by modifying the hmtl code of the blog (and how)?