What exactly is the requirement? Do you wish to disable the background task? This option was never available in default installation of InDesign
1. Create blank text file “DisableAsyncExports.txt”.
2. Place it in:
MAC OS: /Applications/Adobe InDesign XX/Adobe InDesign XX.app/Contents/MacOS/DisableAsyncExports.txt
Win: C:\Program Files\Adobe\Adobe InDesign XX\DisableAsyncExports.txt
(that said, path where your ID is installed).
3. To get things back, just remove/rename that text file.
Didn't test this in latest ID, but it works in earlier versions, so worth to try.
I was thinking wrong too, for me this option was not obsolete. Because, I don't know why, but I remember saw disable background printing appears in the file menu after this "hack" text file been in my InDesign app.
Doesn't seem to be working in InDesign 2021.
Is there any other way to disable background PDF exports?