Laying down bass & treble lines within same measure?

Is there a way to create guitar tab for fingerpickers such that there is a bass line (of quarter notes for example) and on top of that you have some treble notes (eighth and quarter) within the same measure? Taken individually, each line of notes would be correct to the time signature (at least the bass line would, the treble line could have fewer notes - but not more than allowed by the time signature).

My experience is that MuseScore counts each note entered to fill the time signature (say 4/4) such that if I enter 4 bass line notes in a measure, things get weird when I go back into the measure and try entering some treble notes (some of which occur between the bass notes). MuseScore tries to create chords and won't let me place treble notes between bass notes, etc.

Right now, I'm at a loss as to how to enter tab for fingerpicking guitar that has both bass and treble lines within the same measure, not to mention for slide guitar as well.