Are you sure you're using a font in InDesign that has those glyphs
available? Not all fonts have them.
Yeah. It is the same font sets I was using in CS6. There are plenty that do not have them, but I rely on sets that do.
And, within the font, is the line-beneath part of the character glyph
itself, or is it a combining diacritic?
If it worked in InDesign CS6, and the same thing doesn't work in InDesign CC, it's probably a subtle bug introduced when the application had to be re-written for Cocoa/64-bit in CC.
I'd report it as a bug here, and go back to using CS6:
The ones that are not working are a combining diacritic. This shift means working in multiple programs since a lot of the curriculum I have developed is in InDesign. The work stream is going to be disrupted by not being able to see it all in once place and moving between programs.
Here are the letters:
Ḵ — 1E34 Latin capital letter k with line below
ḵ — 1E35 Latin small letter k with line below
G̱ — 0047 Latin capital letter g + 0331 Combining macron below
g̱ — 0067 Latin small letter g + 0331 Combining macron below
X̱ — 0058 Latin capital letter x + 0331 Combining macron below
x̱ — 0078 Latin small letter x + 0331 Combining macron below
@xhunei – Do you test with the latest version of InDesign CC v.9.1.0 ?
I tried it today and Creative Cloud says it is up to date. The trial just expired, though, and I closed it. I cannot tell you what the version number was.