Silkypix. It may be available for download on the Panasonic site. If not, google "Silkypix Panasonic".
EDIT - Apparently it's now PhotoFunStudio, available for download HERE.
I have Photo Fun Studio and don't care for it. I find it inadequate for even simple editing, I can't figure out how to select only photos from a specific date or not yet downloaded for transfer to PC.
Is there a photo program for LUMIX 4/3 like there is for Nikon
I use Lightroom Classic, which supports most, if not all, Lumix cameras. Mac users can use Photos, because MacOS also supports most Lumix raw files. Adding the Raw Power app/plug-in for Photos expands that capability.
The Photos app that is part of Windows 11 can open and "develop" LUMIX files.
Many programs can open RW2 files, the RAW format used by Panasonic with its Lumix cameras. For example, IrfanView and h Adobe DNG Converter can open RW2 files and then save them in various other formats, such as JP2 (a losslessJPG format). --Richard