 The problem seems to happen both with: + the until now working version of blikblum virtual treeview I had on storage + the one shipped with Lazarus (I updated everything Lazarus, LCL, Cocoa yesterday) (One small annoyance is that the blikblum and lazarus versions are not always sync'ed) For completeness here is the thread in the Lazarus Cocoa forum: [https://forum.lazarus.freepascal.org/index.php/topic,53347.0.html](https://forum.lazarus.freepascal.org/index.php/topic,53347.0.html)