Since InDesign doesn't have Serbian and Macedonian languages

…it means those languages’ .locl glyphs won’t work. Stylistic sets seem to be a solution. I think manual (or a blog post) should mention that.
This matters because SRB/MKD has 4 Cyrillic letters that are stylistically different when upright and additional 5 in italics.

I have been planning a blogpost on Serbian Cyrillic for a while. Can you point me to a good resource on this or send me your own samples? mekka at my username dot com

Alexei Vanyashin has a couple posts on Serbian Cyrillic:
http://learncyrillic.tumblr.com/tagged/Serbian

I believe I used some other sources, but I don’t seem to have them handy.

Scroll to the middle

Wikipedia

More

At the bottom

My sample

In addition there’s all this Bulgarian business going on.

Thanks!

The only difference between SRB and MKD seems that MKD italic /sha doesn’t have a bar.

@Eames
Moreover the optional bottom bar in Serbian /sha is becoming a rudimentary feature. Can be found in a few old-style serif fonts, but is rare in local-manufactured fonts, especially grotesques. Fonts made outside Serbia keep including it in fear or appearing ignorant without realising the local preference has changed.

Macedonian uses ѓ, which requires a locl variant. Serbian alphabet doesn’t. This can be solved via mark positioning, if ge-cy.loclSRB has a proper top accent. For the sake of proper semantics I would make a separate MKD glyph for it:

script cyrl;
language SRB;
language MKD;
sub be-cy by be-cy.loclSRB;
sub ge-cy by ge-cy.loclSRB;
sub de-cy by de-cy.loclSRB;
sub pe-cy by pe-cy.loclSRB;
sub te-cy by te-cy.loclSRB;
language MKD;
sub gje-cy by gje-cy.loclMKD;

Sample from Cormorant Italic by Christian Thalmann, Catharsis Fonts.

Serbian can work in Indesign via custom inx files: