Using filters there is an issue when trying to open MLT-files in different systems:
Windows path to filter is similar to
X:/Program Files/Shotcut/share/shotcut/qml/filters/webvfx_threejs_text/threejs_text.html
while this is not found in MACOS since it should be like
/Applications/Shotcut.app/Contents/Resources/shotcut/qml/filters/webvfx_threejs_text/threejs_text.html
Workaround: edit *.mtl as *.xml and substitude path-prefix.
Shotcut should automatically convert the project containing paths for HTML filters to the new path for your system. There was a fix for this in the latest version 20.04. It does this in memory when you open and will not show in the project file until you save.
Does not work for me? Even opening while ignoring the missing path and save over does not solve… I see you have an eye on it, so solution may come, meanwhile I`m using workaround. Screenshot from OSX