When opening/selecting with right-click a model in the OneClick console, it takes a long time until something is happening. It seems that Spectrum is checking the UIM integration code, even if there is no integration to UIM (grayed out).
By commenting out the lines in the "nimsoft-app-config.xml" file ($SPECROOT\tomcat\webapps\spectrum\WEB-INF\nimsoft), this delay is not seen anymore and can be used temporarily as a workaround.
Identified the code and changed it for improvement of this action.
As 10.3.1 is in final stage, these changes are planned for the next release after 10.3.1.
Same issue can be seen for Alarms as well, without workaround. i.e Right Click on Alarms, menu will display which is taking more time to render. For both scenarios a fix is planned for the release after 10.3.1.