Hi,
Knowage is an application composed by a Java app, deployed on Tomcat, and a DB, deployed on MySQL. If you browsed at the URL:
http://localhost:8081/knowage
It means the HTTP connector of Tomcat is well configured. The problem is on the DB side or on the connection between Tomcat and the DB.
If you chose to use an embedded version of MySQL, the link that the installer created on your desktop will launch bot MySQL and Tomcat. If you chose to use a custom instance of MySQL, please check users, grant and the presence of the DB of Knowage.
I don't know what you are talking about when you write "I've changed variable Catalina path" but if you set some environment variables, for example, CATALINA_HOME, CATALINA_BASE or CATALINA_OPTS, watch out that those variables are read by every instance of Tomcat installed on your system: that's the expected Tomcat behaviour because those variables should be used only on certain type of installations.
See: https://tomcat.apache.org/tomcat-8.5-doc/introduction.html#CATALINA_HOME_and_CATALINA_BASE
If you are just trying to run Knowage and if you don't have a system with multiple Tomcat instances, you don't need those variables, they only create problems.
Just revert everything you did to let Tomcat 10 run. Install Knowage, replace 8080 with 8081 in server.xml and run Tomcat, that's all our other users do in your situation.