Installation is a bit of a pain.

How to install:

• Download the SQL Workbench/J zip and manually extract it to something like C:\Program Files (x86)\SQLWorkbench-J (no spaces!)
• If it's not installed yet, download and install the Java SE Development Kit (JDK)
  • It should be in a folder named something like C:\Program Files\Java\jdk-24\
• Use these instructions to change the system-wide environment variables.
  • Set JAVA_HOME to be something like C:\Program Files\Java\jdk-24\bin\
• Double-click SQLWorkbench64.exe to start it.
• You'll probably want to "Pin to Start" on that .exe also.

downloading JDBC drivers

(the official documentation is here)

These should be extracted and placed into the subfolder C:\Program Files (x86)\SQLWorkbench-J\JDBC Drivers\.

• DB2 driver ("db2jcc4.jar")
  • The download for this is hard to find. It can be downloaded from here.