I'm sorry I don't know how to answer your question but I can suggest stories similar to Solo Leveling like:
-The Beginning After The End
-Ranker Who Lives A Second Time
-Tomb Raider King
-Tower of God
You can read them here (=・ω・=)
I asked a question like that before, it may help you as well. What you can do to find similar recommendations for Solo Leveling is looking through tags or looking through lists. Otherwise you can just ask it in the questions, like you’re doing now.
http://www.mangago.me/home/mangatopic/6552490/
http://www.mangago.me/tag/
Yumiko has a really good action list, so I’m sure he might find something he’s interested in.
http://www.mangago.me/home/mangalist/626481/
Here's a list of things related to solo leveling
http://www.mangago.me/home/mangalist/676093/
I'm kind of confused on what you're asking but there is a tag system that might be helpful
http://www.mangago.me/tag/
for example if you wanted to read every story tagged "OP"
you would search http://www.mangago.me/tag/OP
Is there a way to search for a specific topic through all the questions? For example I want to find manga like Solo Leveling for my husband to read, that was his first read, and now he’s hooked. I’m willing to pay for it if it’s not available on here if it’s good