Hi Bruno,
you can install both Royal TSX V6 and Royal TSX V26 simultaneously by choosing “Keep Both” when installing a different Royal TSX version as shown here:
However, since Royal TSX V6 and Royal TSX V26 use different plugin versions, you’d have to reinstall the plugins each time you switch between both apps via the Royal TSX Settings.
Alternatively, you can quickly do this by copying the installed plugins folder to a different path and swapping the content of the folder each time you change the app version. (~/Library/Application Support/Royal TSX/Plugins/):
I hope this information helps!
Best regards,
Christoph