If you are using a recent version of Lazarus, you should be using the DockedFormEditor package instead of the Sparta one. Sparta has been replaced with the DockedFormEditor package.
Ok, thanks, what about AnchorDockingDsgn? Should I keep using it?
2.2.0 is it a recent version? I've installed it using apt-get lazarus on Linux Mint.
P.S.
I installed AnchorDockingDsgn but nothing has changed, plugin settings in Tools/Options don't show anything useful
I don't consider 2.2.0 to be very recent. I have 2.2.4, 2.2.6, and 2.3.0 (trunk) on my system. All of these work pretty well using:
AnchorDocking, AnchorDockingDsgn, and DockedFormEditor.
I don't normally have the Project Inspector docked, but it can be done. See attached image.