From Arctis version 1.0.0.M0341 you can edit activities without using the palette. Just use the context menu. In case you want to de-select an activated tool, just use the ESC-key. For now, the context menu makes the same functions available as the palette, but we will add more context-specific actions in the future. Try it. You can save a lot of movement with the mouse pointer!
You can de-activate the palette altogether using the Preferences under Arctis / Editor. For COCOA-users on Mac OS the palette is not shown anymore to minimize errors of SWT on Cocoa as documented in Bug 323670