This behavior is as designed. When you start the TIBCO Spotfire installed client it creates a lock file in the Spotfire Lists directory which prevents any other Analysts from working on the list files.
A workaround is to use the TIBCO Spotfire Analyst portable client which has been extracted to a different folder, and then use that to have another instance of the Spotfire client running. This is available for download under the "TIBCO Spotfire Analyst" product on
https://edelivery.tibco.com. If you run the TIBCO Spotfire Analyst installed client and the TIBCO Spotfire Analyst portable client at the same time, they will then both be able to manage list and tags.