I thought I had got Cairo-Dock working fine after finding that I needed to install the cairo-dock-gnome-integration-plug-in but suddenly for no apparent reason I can now not edit any icons on the dock which partly negates the reason I use a dock, I.E I can make it look just how I like it with the use of my own personal icons.

I tried a complete uninstall & reinstall but nothing has changed, Oh & I seemed to have lost the recycle bin icon too.

I can't seem to find a contact email address for the developers or much helpful info on the web.

I'm using it with stock icons at the moment & it works but it doesn't look good.

I never had these problems in Mint 18.3 so I wonder if it's not fully compatible with Mint 19.

The warning on the Linux Mint website is don't upgrade to Mint 19 unless you have a good reason to do so & they point out that 18.3 is supported until April 2021.
Well I now know I should have paid attention to that warning & it's a lesson learned.

I had a few issues with 19 & I spent some time trying to resolve them until I realised I had no previous issues & so I used Timeshift to revert my system back to 18.3 & now my system works fine.

Maybe in a few months when the bugs have been found & fixed I may have another go. I am sure that there will be many people who have upgraded & not had problems but of course this depends on what software you use, for now I will just continue as I am.

There is an easy workaround. Right-click on the Cairo dock and select Cairo-Dock->Configure. Then click on the Current items tab and expand the relevant dock. You can then edit an individual menu entry. The old right-click was just a short-cut to achieving this. You get used to the new method very quickly.

Well I will keep that information to hand but I have now reverted to 18.3 which is working fine. as I say maybe I will try again with 19 at some time but for now I'm heeding the warning.
As always thank you for your constructive input hydrurga.