If you want two switches (one for each drive) then you dont need diodes. Thats only if you want one switch activating both drives at the same time.
Your only issue is finding the switches that will work for your throttles. You want to find momentary ON/OFF/ON switches and wire them in parallel with existing switches on dash.

Are the components (switch and cover )for the dts zero effort lever not the same ? I dunno. Just throwing it out there

https://www.marineengine.com/parts/m...ts-1-2-3-lever

Another thing, i reconfigured a Teleflex MY control (4 lever) the other month and they look near identical to the zero efforts. Not sure if they offer trim switches and covers for the controls.

http:/www.boaterstore.com/teleflex/mycontrol.pdf

and

https://www.marineengine.com/products/technical_information/iMYi%20control.pdf

Same part number. We have a winner!!

Same part number(s). Can get the switch with wiring or the whole thing.

Probably a pain to try and use one on each side. What do you guys think?

When you say helm I'm guessing you mean on the wheel?
You're current trim switches are on the dash?
I'm a fan on the one on the throttle trimming both drives together then just using the dash switches if needed if they are out of sync.
Anything is doable and all subject to opinion but seems one of those switches opposite side of your thumb would be cumbersome.

I would use one switch for both drives and use diodes.

Yep, switches are on the dash and pretty hard to get to when things get rough at speed. Having the switch on the throttle will make things much easier/safer.

I think I’ll start with the one switch and diode combination. I may add another for the tabs, but if I do, will be down the road.

I’m going to order the Merc switch.

Ordered the switch assembly and the Marine Industries West diode kit. Let's see what the switch assembly looks like when it gets here.

Watching and learning as I too would like a set-up like this.