Custom Tags can be managed through the Custom Tags manager at:
Custom Tag Editor is located at CP -> Content Rebuilder -> Custom Tag Editor

As for the style editor the elements are broken down by page, this particular item is for the markup panel which has its own section "Markup Panel Properties" and the dropdown would be located as:
.markup_panel_popup
.markup_panel_unselect_text
.markup_panel_select_text

I am a Web Development Contractor, I do not work for UBBCentral. I have provided free User to User Support since the beginning of these support forums.
Do you need Forum Install or Upgrade Services?
Forums: A Gardeners Forum, Scouters World
UBB.threads: UBBWiki, UBB Styles, UBB.Sitemaps
Longtime Supporter & Resident Post-A-Holic
VNC Web Services: Code Modifications, Upgrades, Styling, Coding Services, Disaster Recovery, and more!