Alt+Drag Duplicate is not working correctly
When you use ALT and Drag to duplicate Objects, the duplicating is canceled if you release the ALT-key before you release the Mouse Button.
Also, if you release the Alt, but don't move the mouse, the original one will be still visible, but it will disappear after you release the mouse button (or move the mouse). So, the Illustrator leads you to assume that the Object will be duplicated, but it actually wont. See the attached GIF.
In every other App that has the same functionality that I have used the duplicating will continue even if I release the Alt key. You alt drag something, you create a duplicate, you release the alt key, duplicate stays.
The way Illustrator does it leads to a lot of errors. Often I end up in situation where I thought I duplicated something, but I actually didn't. Frequently, I edit the “duplicated” object, only to find out later that I didn't actually duplicate the original one, but loosed it. Then I have to recreate it, as I have edited the duplicate one and don't have the original any more.
This error in basic functionality of Illustrator has cost me probably hours of extra work.
Lingojigari Sameer commented
alt and drag are not working in Illustrator
An earlier general request to change the duplication paradigm: https://illustrator.uservoice.com/forums/333657/suggestions/44954005
Please vote there.
This particular report is going to be reviewed as a bug report about the ghosting issue.
Yes, it’s a known and the old paradigm Illustrator uses (along with InDesign, XD, and Figma) — all modifier keys affect the result only if they stay pressed until the mouse button is released / pen lifted.
Compared to the one Photoshop uses (and some other apps like Affinity Designer), it has some benefits. The main one is that you don’t have to start holding Alt strictly before you start dragging.
Some other apps like Corel Draw or Inkscape don’t use this Alt-to-duplicate method at all.
But really, it the same exact treatment Shift or Ctrl/Cmd modifier keys get — you can start or stop holding them at any moment, and Alt is just another one.
It most probably won’t change in the near future. If you still want for it to change (or better to be customizable) — please log it as a feature request.
As for the bug with the drawn copy — yes, it is a GPU bug. Definitely needs fixing!(Edited by admin)