Anyone know where to find/download sample MASKS, *.dem for TDBEdit - EditMask property?
You've found a bug/missing file(s) in the IDE.
The property editor says it uses .DEM files for sample edit masks. None are provided.
The code for the property editor tries to load maskeditmasks.txt from the primary config directory. That file does not exist.
Please report the issue to the Lazarus bug tracker. (link on the left).