If the Add-in tab is not showing, close PP, and try going to the Control Panel > Programs and Features > Camtasia 2018 > R/click > Change > Modify > Make sure PP is Enabled.
Open PP for a comparison.
If that doesn't work, a Repair might help.
I note you are using a 64-Bit version of Office 2010 - there might be an issue there regarding the PP Add-in?
There’s this Youtube video to show you where to enable the Add-in if it has been disabled: