Operating system: windows 10
Graphics card: nvidia geforce
Broken: v 2.81a
Short description of error
The python API docs claim that custom properties will be saved with the blend file, but this does not appear to be the case for custom properties defined on workspace objects.
Exact steps for others to reproduce the error
from default startup (new general file),
open the active tool and workspace settings panel (screwdriver and wrench icon)
open the workspaces sub-panel
add any custom property
save the file
close and re-open it.
(the custom property won't be there)