We are on the same page here @Martchus i think your tray is the right apporach.
I don’t know much about GTK or QT development but i imagine that it is much much harder to make it than web ui. Synthing is going to have lot of options and doing it weby way seems the most flexible.
I am not 100% sure but considering the fact that you’ve made the GUI fast using Qt then it is not a problem of the Syncthing or the api. It is problem of the UI. A while back I tried digging into the angular 1 project that syncthing uses and it is crazy. Angular 1 is unfortunately probably the slowest framework there is. It is also completely dead. Angular 2 is completely different framework requiring complete rewrite if you want to upgrade.
I am pretty sure the web ui would be way faster if it was written today with current tech.
Working on the webui now is probably huge pain and not fun. Rewrite is also a huge task. I guess project is just stuck with it. I am pretty sure core devs want (and should) to put time into the syncthing itself not into javascript ui.
You could probably find some webdev person who would rewrite the ui IF the UI was problem for them when using syncthing but… i believe majority of the people don’t use the webapp too much. It’s more like gui for text config.