I just thought about this maybe being useful, but I can't find a way to do it.
Is there a way, in Notepad++, to make function names "clickable" -- ie make them links, so that if you click on them, it automatically takes you to its definition (ideally across an entire code-base)?
At the moment there's no plugin offering directly clickable function names. But you could try the plugin SourceCookifier together with some N++ tweaking. Open N++'s "contextMenu.xml" and add this line somewhere:
<Item PluginEntryName="SourceCookifier" PluginCommandItemName="Go To Definition"/>
At least a solution to have it with 2 mouse clicks > right click > contextmenu > "Go To Definition". I would rather say simply press CTRL + SHIFT + RETURN when the cursor is on a symbol, which also executes "Go To Definition", but since you asked for a mouse button approach..
/EDIT
There has been an update of the plug-in these days. Here's a snippet from the changelog:
0.7.1
-new: option "Go to definition by pressing ctrl + left mousebutton"
