Hello @oleg_petcu 
Apologies for the delayed response.
Our developers have been made aware of the issue, however, since DevKinsta is still in security updates mode, we don’t have an ETA on when this will be fixed.
While it is not ideal, please use the workaround you shared above where you select any of the files from the root to be able to partially select files from wp-content.
Our developers are aware of this and will be working on this issue and other improvements to the DevKinsta in the coming months.
Thank you for your patience and understanding. 