Can't drag and drop the object any longer

Hi, I am a newbie of Shotcut. This is a great app for video editing. While I have been working on my project, I found that I can’t drag and drop the object any longer. Here is the screenshot.

What do you mean by this? Are you talking about adding new items to playlist of adding new items to Timeline (from playlist)?

If you’re talking about what I think you are, it’s a known issue that crops up from time to time.
Save the project, close Shotcut then re launch Shotcut and open your project. This should fix it.

I agree with @Steve_Ledger. I notice that the OP has exported two jobs in the screenshot. For me just that alone creates instability issues where Shotcut doesn’t work right. It’s a minor bug to me, but I can’t make it happen. It doesn’t happen that often which is why I never. It’s never stopped or crashed at anything specific that I can think of though. My fix has been to just save and restart. If it does crash, Shotcut opens right back up to where I left off, sometimes it might be missing the very last action I took before it crashed. Again this is so minor it doesn’t bother me.