how to allow only 1 out of the 3 exposed filter to be selected

Hey Monaw,

disabling filters in the way the html attribute "disabled" would do for a "vanilla html input" is not supported by this module, but that is due to the fact that exposed filters and their html-structure can also be extended or manipulated in any thinkable way.

Though you can easily hide/remove the filters with this module accordingly so that only 1 of the three filters can be chosen at a time.

Lets assume your "active value" is the string "on" and dff1=compound,dff2=mass,dff3=formula
then, for example, you could use the neq condition (not equals) on the compound admin lable like:

dff2|{neq:on}|AND|dff3|{neq:on}|

This way the compound filter will only be shown if neither mass or formula is selected. You can use the same logic for the mass and formula input as well and achieve your desired behaviour.

PS: Sry for the late reply, i´m on a longer family getaway, hope my answer still helps you