Set Windows environment variables directly in wsl shell without modifying bash environment

Is your feature request related to a problem? Please describe.
Suppose the user wants to set windows environment variables from wsl.
In the current mechanism, the user needs to first set a bash environment variable, then export it as a windows environment variable via WSLENV. The problem is that this defines environment variables in the bash shell as well.
Suppose that the windows environment variable has the same name as a bash environment variable.
Currently it's impossible to set one value for bash shell, and a different value for windows environment.

For example:
suppose we want to set "TEMP" windows environment variable from wsl.
The user has to do:
export TEMP=...
export WSLENV=TEMP/w:...
The problem is that this will modify the value of TEMP environment variable in bash shell as well.

Describe the solution you'd like
We need some mechanism to set windows environment variables from wsl without modifying the bash environment.

Something like:
win_env_set TEMP = ...

Describe alternatives you've considered

Additional context

The issue names no files, tests, or entry points. Start by tracing the existing WSLENV mechanism described in the report and determine where Windows environment variables are transferred. Done should allow setting a Windows variable from WSL without changing the same variable in the Bash environment, with coverage for the TEMP example.