Use variable inside other vars default value

My Base URL has been changing a few times, Going over every item inside the namemapping to change the IP address to the website takes a while.

So I want to make my BaseURL inside the namemapping a variable.

To do this I found it's not possible to concat inside the namemapping

^ This doesn't work.

Then I thought lets just a var for each of the programs.

However I quickly found out that works for the entire run but not when running individual tests because those vars don't get set.

Is there any way to set the Default value with a variable and concat the appropriate link to it?

This is my current namemapping:

I want to set it like this or something similar:

Using the vars with a default value to also be able to run each test individually for debugging.