How to unattach imported PST package

Dears,

i have imported the big PST package file into emClient under local folder section. However its way too big and i need to free some disk space now.

So the question is how to unattach the PST import completely. I will just keep the PST source again.

My eM Client is 8.2.1687 (bf522f0) - macOS

Thank you very much
Martin