Capes VS pacmc

Sadly no. BUT there is a client side mod called capes which let's players have custom capes but you have to have the mod to see other players custom capes

After a quick search I found this mod called Fabric Capes, which might be what they're talking about

Fabric Capes (by VictorKohler)

You can install Kappa or Fabric Capes alongside sodium/iris for optifine capes

You can replace all of Optifine's features with the right Fabric mods, like Continuity, CEM, Animatica, FabricCapes, and Iris. I don't know all the features Optifine has, but every important feature Optifine has that I can think of has a Fabric mod counterpart.

Well, there is the Fabric Capes mod, it shows capes from OptiFine and a whole bunch of other mods

you can get to see your capes in fabric, just add this mod https://www.curseforge.com/minecraft/mc-mods/capes :)

It invokes that native file picker dialog on each platform, currently supporting Android, and Desktop (Windows, Linux, osX) using lwjgl and thanks to the work in the pacmc project.

Kotlin/JVM: LWJGL has native file dialog (NFD) bindings, here is how I used them with fallback Swing file chooser with native look and feel.

There are some open source launchers with that feature. I think at least Gdlauncher and Atlauncher have built in mod management (and probably instances as well). But I prefer to use a package manager for MC mods called Pacmc. It is not super fast like Pacman, but it works really well for managing MC client or server mods (I use it for both). The only features its missing for my use cases are disabling automatic dependency management and installing mods that are not marked as compatible with latest minecraft versions, but work just fine. Also it seems like the author of Pacmc is working on a gui right now.