https://site.ru/index.php?route=bossblog/article&blog_article_id=1
https://site.ru/blog/1
RewriteCond %{QUERY_STRING} (^|&)route\=bossblog/article($|&)
RewriteCond %{QUERY_STRING} (^|&)blog_article_id\=1($|&)
RewriteRule ^index\.php$ /blog/1? [L,R=301]
RewriteCond %{THE_REQUEST} ^\S+\s+/index\.php\?(?=(|.*?&)route=bossblog/article[&\s])(?=(|.*?&)blog_article_id=1[&\s])
RewriteRule ^ https://site.ru/blog/1? [R=301,L]