Visual Studio Code: can't edit LEFT-side file during COMPARE

In Visual Studio Code I open file-VS-file compare mode via:

• clicking on the file A and then "Select for Compare"
• clicking on the file B and then "Compare A with B"

The problem is that I can edit file B (RIGHT side), but can't edit file A (LEFT side).

Edit: this should be working out of the box in vscode version 1.41.0

It will show Unknown configuration setting but it's working.

"diffEditor.originalEditable": true