Variable font and custom parameters on instances

Is possible this is not working? I have a one-axes variable font with a custom filter parameter on instances and it isnt applied on variation TTF. Should I have to add this filter on Font Info or maybe masters? What I am doing wrong?

Thanks!

Filters are not supported for variable fonts, yet. What exactly are you trying to do?

Just a filter to round the font just a little… but I can apply it manually, or there is another way?

Corner components work. Instead of a serif, you draw the rounded corner. Added advantage: gives you more control over the rounding.