app.refresh();

redraw, as far as I remember, was an ActionManager equivalent of refresh, that can be used in older PS versions – same concept, though.

I need app.refresh() for opening smart object content and "while" loop comparing active document with last opened or custom $.sleep() didn't worked for me. It was stucked in endless loop.

I noticed that there is Kevlar API with Idle event. How it works?

Photoshop Kevlar API Additions for Generator · adobe-photoshop/generator-core Wiki · GitHub

I'm afraid that if you really need app.refresh(), you have to bear with the extra slowness that said refreshing implies.

Why you need app.refresh() ?

The only thing I can think of is to have Photoshop refresh only what the user needs to see and use.  For example toggle all palettes off so Photoshop only needs to refresh the image being worked on.  Pallets do not need to be refreshes for they are not being displayed. And only use app.refresh(); when the user need to see the current image and do something. Like an interactive transform or select an image file etc.