The bad news is that it doesn't work too. I have added it, closed geany, reopen and all is the same.
<details> <summary>WFM, looks like that:</summary>
Default: ![default](https://github.com/geany/geany/assets/793526/73d4a2cd-639d-46bf-8ff9-dd28c7e...)
Adding `lexer.bash.styling.inside.string=1` ![strings](https://github.com/geany/geany/assets/793526/4e5ffde0-6a55-43bf-9376-da839dc...)
Adding `lexer.bash.styling.inside.backticks=1` ![backticks](https://github.com/geany/geany/assets/793526/dbab43a5-d112-4659-86c4-4957880...)
Adding `lexer.bash.styling.inside.heredoc=1` ![heredoc](https://github.com/geany/geany/assets/793526/7e0ffa47-bb6a-4447-bafa-35f5ab7...) </details>
One question: what is the correct: altering via Geany Tools, ... or editing directly in the file /usr/share/geany/file...
Because opening in Tools, all lines appear commented and is is different from the same file in /usr/share/geany/file... What is actually used ?
Both are used together. If something is not defined in the user's configuration, the value is looked up in the /usr/share one (or whatever the Geany installation path is).
All you need to do is go through Tools… and replace the whole content with literally what I mentioned above. Or add it (uncommented) somewhere.