Hello,
As mentioned here :
https://community.qlik.com/t5/New-to-Qlik-Sense/Selection-in-edit-sheet-mode-April-2019-not-availabl...
it was a nice feature expected in April 2019. And then it just disappeared from QS.
Basically, the idea is to be able to select value when editing a sheet. It allows to gain a lot of time in design step, especially when you want to test the behaviour with set analysis, total, aggregation...
Best regards,
Simon
Bi Consultant (Dataviz & Dataprep) @ Business & Decision