Measured arpeggio, how to notate it?

So, I have made some decent progress with my bagatelle, but there is something that I know I want but am not sure how to notate in Musescore(or even if it is possible). That is a measured arpeggio. Let me make things clearer. What I am wanting is something like this:

Except that instead of the 32nd note distance in the arpeggios shown above(which are from the Presto Agitato of the Moonlight Sonata), I am wanting an eighth note distance and I am wanting all the notes of the arpeggio tied to a half note. Also, as far as notes and how many of these arpeggios, I want 2 arpeggios, the first of which goes Bb, D, F, Ab, and the second of which goes Eb, G, Bb, Eb. If I want to lengthen the arpeggio to 3 bars, that's easy. I just go into note entry mode, make sure the half notes tied to the measured arpeggio are selected and then press the plus key and I will have lengthened the arpeggio.

The hard part is getting the measured arpeggio in the first place. A measured arpeggio is easy when you don't want to sustain the notes of the arpeggio across the entire arpeggio. It is hard when you do want to sustain the notes of the arpeggio across the entire arpeggio as I do in my bagatelle. As you can see from the Presto Agitato arpeggios above, there are 2 beams per note, 1 beam for the arpeggio in its entirety and another beam for the individual notes. Best way I know to get that is by having the first and second voice in unison and then making all the second voice notes silent.

But, I'm not sure that I can do that, because there are 4 voices in total in the Musescore software. Won't putting all the eighth notes in the first voice and then tying one of them to a half note cause the other eighth notes to disappear? So that would mean that I would have to use 4 voices for the eighth notes. Then how am I going to get my 4 eighth note beam? My bagatelle is at the bottom of the page and the arpeggios would start at measure 119.

How can I notate this sustained, measured arpeggio in Musescore(This would also help if I ever finish arranging the Moonlight Sonata for string quartet)? I have only seen such precise arpeggiation notation for sustained arpeggios in the Presto Agitato of the Moonlight Sonata, thus me using it as an example of measured arpeggios. Most sustained arpeggios that I see are notated as an arpeggiated chord, but I am wanting more precision than that with this bagatelle, thus me asking how to notate a sustained, measured arpeggio in Musescore.