[TONE CURVE] Tabs are hidden if you expand the module later
If you use the tone curve module and select e.g. "Lab, independent channels" you will get tabs for the 'a' and 'b' channel. If you now do a change e.g. do the 'a' channel, collapse the tone curve and apply another module. If you then expand the tone curve again the 'a' and 'b' channel tabs are hidden, you have to re-select 'Lab, independent channels' again!