Created attachment 139589 [details]
Improve Adding/Removing columns

To add a columns in system monitor you should right click on header then you will see a pop up with list of items, to show any specific column you change it from Hidden to another, and you can grab it and move it to top or let it in its place, the first problem is that the list of columns in that pop up is not sorted, so it's difficult to search for specific column and you should read all of them, secondly if you enabled a column to be shown and didn't change its position it's really difficult to search for it in that long list.
The columns adding and removing experience in KSysguard is way better and user friendly than in the new monitor, what would be appreciated is to make the list of items in that pop up separated in two region, the first contains the list of visible columns witch ability to grab and sort them, and the second region with list of non visible columns sorted alphabetically to make it easier for user to search for specific items. See image1 for more details.
The finally wish to make easier for user to use new monitor is allow reordering columns by grabbing columns headers like in KSysguard instead of showing that popup to make simple reorder.