Settings for opening the 3D Shape Search at the very first time are taken from the default template.

The respective setting can be found in geomsearch.cfg > block [SEARCHTEMPLATES ] > key DefaultTemplate. This template is using SizeDependent=0.

For example, if you want to activate the option Include Part Size by default, then use the value SystemTemplate7. In this template the key SizeDependent is set to 1.