Add a hotkey / intent to jump from the preprocessed file in versions/<version>/build/preprocessed/(.*) to src/$1.
For the reverse of that jump, maybe a little popup could show up with the possible destinations to select from.

Sometimes, especially in imports, #if directives may be nested.

Example:

//#if FABRIC
import net.fabricmc.api.ClientModInitializer;
import net.fabricmc.loader.api.FabricLoader;
//#if MC >= 1.18.2
import dev.isxander.mainmenucredits.MainMenuCredits;
import dev.isxander.mainmenucredits.config.MMCConfig;
import dev.isxander.mainmenucredits.config.MMCConfigEntry;
import io.github.gaming32.worldhost.gui.OnlineStatusLocation;
//#endif
//#else
...

Currently this plugin does not fold this, and may even display weird errors regarding mismatched #endif directives, despite them not being mismatched.

When inserting a new line like so:

//$$    fun onInitialize() {<cursor here>}

there are no new $$s on the next line after pressing enter:

//$$    fun onInitialize() {
// }

I think the $$ insertion is from this plugin

Something like //$$"1.14.4" gets highlighted like so:

I think that " should not be highlighted.

Having IntelliProcessor enabled breaks Optimize Imports, even in projects without the preprocessor.