Yes, you can do the same for testsuite to be exported and then added to testplan's test suite section.
For example, test plan was created in GUI and its id is 5, then
you can use: testsuite.testplan=LinkExisting("urn:com.ibm.rqm:testplan:5")
in your cfg file to export testsuite into RQM and add it to the test plan:5
A quick test can be done against the sample TestSuite with TestCases 001.xls,
in TestSuite with TestCases 001.cfg, you can comment out test cases related and only use testsuite creation part and
add the above link to cfg file, it will be like:

// this configuration file will create a static testsuite and a testcase object for each one listed
// and link all testcase to the testsuite


testsuite.dc:title=C1
testsuite.dc:description=A4
testsuite.testplan=LinkExisting("urn:com.ibm.rqm:testplan:5")


//testcase.XLSStartRow=7
//testcase.XLSArtifactID=B
//testcase.dc:title=B
//testcase.dc:description=E
//testcase.jzalm:owner=C
//testcase.Section("myns:com.ibm.rqm.planning.editor.section.testCaseDesign","RQM-KEY-TC-DESIGN-TITLE")=F
//testcase.Section("myns:com.ibm.rqm.planning.editor.section.testCasePreCondition","RQM-KEY-TC-PRE-COND-TITLE")=K
//testcase.Section("myns:com.ibm.rqm.planning.editor.section.testCasePostCondition","RQM-KEY-TC-POST-COND-TITLE")=L

you will need to change the testplan id to your real one for it. In my case, it is 5.
if your testplan is also exported from ExcelImporter, you should use external id when exporting testplan. In that case,
using a column in xls file to specify external id and then testsuite.testplan=LinkExisting(C)
(C is the column you have testplan external id specified)

Hopefully this helps.