delete project level custom property

having added properties multiple times with 

testRunner.testCase.testSuite.project.addProperty ("mPropertyName")

I ran the same problem.

Running the command

testRunner.testCase.testSuite.removeProperty( "myPropertyName" );

doesn't help - the number of custom properties in my environment remains unchanged.

Removing the properties manually doesn't work - I get a pop up asking me to confirm "Remove the selected properties?" and when I click on "Yes" nothing changes (seems to be a bug, please correct me if I am wrong)

Trying to export the properties yields an error message - it says "No properties to save!" (?)

If I create a single, new property, run the export and then an import with the option "Delete remaining" checked, nothing changes. (this process seems to be buggy, or I am missing some point)

The only solution I could come up with so far was to rename the environment, create a new environment with the old name and then removing the old, renamed environment, which is very cumbersome.

Getting desperate... any help on this would be MUCH appreciated