Thanks, Gino, for providing this information!
To do this:
For example, in the above tool, you could use the following series of key-ins :
place cell icon (to start the tool)
set item toolsettings cellinteractiontype=1 (to set the interactive option)
set item toolsettings celltypeinteractivetoggle=1 (to enable the interactive toggle)
This can also be done in the Customize dialog when making custom tools by right clicking in an empty area and adding item settings:
I've removed the //. They were used to delininate the comment from the command.