Duplicating a control in a window with many controls takes ages.
Does copy-paste work faster? Wondering if this is the same bug as FB# 43306
Copy-paste is faster. But duplicate freezes whole window - mouse cursor disappears for some time.
Sounds like the same issue or at least related somehow. I noticed it when duplicating methods in a module with >100 methods.
Make sure you submit a Feedback report. If you’re on a Mac you should see if you can get a process sample (via Activity Monitor) and attach it to the Feedback report.