Processing 3 text editor running slow

@paulgoux visual studio on RaspberryPI, I don’t think so. I have a RaspberryPI4 and have installed the development version of processing4 (on Manjaro 64 bit distro). The processing ide is a resource hog, but probably not as bad for me as @Tromba see memory usage below:-

Compared to a simple sketch

It should be possible to use vim or even geany as your processing environment. I use both when developing my PiCrate sketches see my recent post.
PS: There is no official support for processing on the RaspberryPI at present.

If you develop code outside processing ide you will need to place your sketch.pde in a folder with same name ie in this case sketch, crap I know but this how processing pre-processor/compiler works. The alternative is to switch from processing to pure java (no pre-processor required), but then you might prefer to look at another processing implementation? Just to get you started with geany, simplest is to just use java syntax highlighting then you need to setup processing-java in the build menu see below:-