Hi, @wally333 
By any chance, do you have your (MATE) clock / calendar in the panel set to display the seconds besides showing the date and the hours and minutes ? If you do, then I suggest that you reconfigure your Ubuntu MATE clock to stop showing the seconds (so it does not have to update the applet every second, which should lower the CPU usage of the process "mate-indicator-applet-complete"). That tip of mine worked for @mickee that had a similar problem and (also) had his clock set up to show the seconds. For more details, please see the following post of mine:
... and the following confirmation by @mickee that removing the seconds from the clock stopped the problem for him:
I hope this helps Please, reply later, in this same discussion topic where we are now, to tell if you have your clock in the panel currently set to display the seconds and, if you do, if reconfiguring it to stop displaying the seconds succeeds in lowering the CPU usage in your computer running Ubuntu MATE 22.04 LTS ("Jammy Jellyfish").