Here is the information from the online Help that talks about Running a Script when JMP starts up that will let your default URL
Run a Script at Start Up
You can run the same script every time you start JMP. For example, you might include the definitions of some utility functions or a namespace that you want available throughout your JMP session. You might also set some preferences in a startup script to keep preferences consistent. Preferences persist across JMP sessions, but you could explicitly reset some preferences in case they were changed at some point in the previous session.
Name the script jmpStart.jsl and place it in one of the following folders, as appropriate for your operating system. When JMP starts, JMP looks for the jmpStart.jsl script in these folders in the order in which they are listed here. The first one that is found is run, and the search immediately stops.
Note: Some path names in this section refer to the “JMP” folder. On Windows, in JMP Pro, the “JMP” folder is named “JMPPro”.
On Windows:
1.C:\Users\<username>\AppData\Roaming\JMP\JMP\19
2.C:\Users\<username>\AppData\Roaming\JMP\JMP
On Apple macOS:
1./Users/<username>/Library/Application Support/JMP/19
2./Users/<username>/Library/Application Support/JMP
The jmpStart.jsl script runs only for a particular user on a computer. You can add a script named jmpStartAdmin.jsl in one of the following places, as appropriate for your operating system. This script is run for every user on a computer. JMP runs jmpStartAdmin.jsl first if found. Then JMP runs jmpStart.jsl if found.
On Windows:
1.C:\ProgramData\JMP\JMP\19
2.C:\ProgramData\JMP\JMP
On Apple macOS:
1./Library/Application Support/JMP/19
2./Library/Application Support/JMP
Jim
