Thank you for your kind response.

Will the installation of the 2.04 client on the 10.9.5 mac affect the functioning of the 1.9.8 wallet, if I just leave the 1.9.8 wallet on the 10.6.8 system as is? I wouldn't expect so, but just to be sure.

Finally, once the installation on the 10.9.5 system is completed and confirmed, is there any point of keeping the 1.9.8 wallet?

I'm new to all this, so I don't want to make a mistake.

I currently run version 1.9.8 under OS X 10.6.8. I have other Macs here running 10.9.5 which do not have Electrum installed.

I have, of course, my 12-word seed generator.

I want to upgrade to the latest version of Electrum, with subsequent use of a Trezor.

Can someone list for me, in clear steps, the way to a problem-free upgrade? Or, is the upgrading trivial, and I'm worried over nothing. Many thanks.