Limiting data from secondary tables in visualisations, calculated values etc.

When you combine multiple tables in visualisations, the only way to limit data from the secondary tables is to use filtering schemes. This makes it virtually impossible to create real "hard filters" when using multiple tables because users can always change filtering schemes (at least as long as TS-I-6285 is not implemented). Furthermore, limiting the data directly on the visualisation axis is cumbersome and not always what you want.

So I'd like to have the option to limit data from the secondary tables in visualisations like it is possible in many other custom expressions. The same also applies to calculated values and wherever you can limit data using an expression, but having the option for the main visualisations is the priority.