⇧⌘H in Bike applies a standard HTML-style highlight.
It’s rendered in Bike as a yellow highlight, and corresponds to the HTML <mark> tag.
See, for example: The Mark Text element – HTML – Mozilla
The yellow highlight in text copied from Bike pastes directly into editors like Text Editor and Apple Mail.
For exporting through Pandoc to MS Word .docx, you can map the Bike highlights to MS Word yellow highlights by referencing a Lua snippet given here: