If you feel comfortable with the syntax of the test plan editor statements and know the locations of the appropriate script and test case, you can enter the script and testcase statements manually.
script: scriptfilename.t testcase: testcasename
Where script and testcase are keywords followed by a colon, scriptfilename.t is the name of the script file, and testcasename is the name of the test case.
If you enter a statement correctly, it displays in dark red, the default color used for statements. If not, it will either display in blue, indicating the line is being interpreted as a test description, or black, indicating it is being interpreted as a group description.