Just installed the cLine script in Moi3, and in Moi2.
Found that the instruction for installing the Icon for ConstructionLine3.zip,
for Moi3beta (windows), needs to be slightly different from the Moi2 version.

Replace empty slot in SidePane.htm:EditTabContent with: (just showing the changed portion because I
forgot how to label code, as code.)

Moi2 version.
...CommandButton style="icon:icons/CLIcon.png;"

Moi3 version.
...CommandButton icon="icons/CLIcon.png"

(Please correct if this is in error)