* Hilighting all matches a selected word/part

Already possible with the "Mark all" keybinding and by double clicking on a word with the Addons plugin enabled.

Hilighting every exact match at message when doing "find document usage"

Should be possible but need to implemented by "someone".

* run external application

Not sure what exactly you mean but Geany can: - compile/build and execute the current file using [Build commands](https://www.geany.org/manual/#build-menu) - execute a configured custom command on the current word and pass this word as argument to the command, see [Context Actions](https://www.geany.org/manual/#context-actions) - send the selected to a configured command as input and replace the selection in Geany with the command's output, see [Sending text through custom commands](https://www.geany.org/manual/#sending-text-through-custom-commands)

* has % geany variable for the selected word/part

I don't understand this. Could you explain what exactly this means?