There’s a few plugins that I’m using that don’t work 100% in Ardour. One of them, PlugData is basically Pure Data as a vst/lv2. You can create patches in the vst itself or open existing ones. However, whenever I try and open a patch via the plugin (loaded into Ardour) the file browser window doesn’t appear.
However the plugins should really ask the host to open a filebrowser, rather than launch a separate tool (which is not realtime safe and may cause dropouts). Both LV2 and VST allow to delegate file selection to the host.