I finally got a chance to try on LMDE6 (my LM21 machine is still HDC).
Remember I said above I was using LM20. In `icons/Mint-Y/actions/*` it has `geany-build`, `geany-save-all` and `geany-close-all` links to `run-build`, `document-save-all` and `window-close` respectively. (@Hund LM20 does not have the "simplified" theme selector, just the "advanced" one, that caused some of the confusion above).
LMDE6 does not have the `geany-*` links AFAICT nor `run-build` nor `document-save-all`.
@b4n Mint-Y does provide quite a lot of icons in the `legacy` subdirectory including`document-new`, but no `geany-` ones so the fallen over bookcase and friends are back. :-( Thats not surprising since looking at the git history it appears that most icons were removed from the `actions` subdirectory then the `legacy` one created from Adwaita `legacy`, sigh. Presumably this is to prevent Adwaita removal of useful (legacy) stuff from breaking Mint.
I guess thats the case for Gnome anyway (except it falls back to Adwaita, so no guarantees anything legacy will remain available).
So if we had "somebody" with artistic talent and taste maybe the Geany icons could be modernised and light/dark and symbolic versions created.
But it seems to me that the whole icons thing is [bleeeep]ed up, either: 1. if an application has any action that a distro/theme doesn't have it can have no icon, or 2. the application picks the nearest available icon, like the links in LM20 above using "near enough" icons and hopes the distro/theme continues to support it, or 3. applications provide their own icons for actions that the distro doesn't support, but they will not integrate with the look and feel of many themes.
This isn't just a LM problem, and I don't have a solution, @b4n do you know what the solution is supposed to be? Perhaps given Gnome HIG says "users must use Adwaita, they are not to be allowed to make any choices" they think thats a solution [end grumpy olde guy rant]?