Is it possible to move SSL from cPanel to Plesk?
Yes, if you have a SSL Certificate for cPanel hosting, you can move it to Plesk. If both your cPanel hosting and your VPS with Plesk is running in the same OS (for example: Linux) then you can use your existing certificate with out requesting for reissue.
If you want it to move to a Windows server with Plesk then you have request your SSL Certificate vendor to reissue the certificate before you can move it to Plesk. Then you just need to follow the same steps again to install the certificate.