In the definition of the staff style for One-Bar Repeat, select that the staff style should show Notes in Other Layers.

Thanks! Sorry, I thought I already tried that.

Yeah, this doesn't work with slash notation as i said in my other post (reply to Peter)

It does work with any Staff Style, including Slash Notation.

Suppose you usually enter your music in layers 1, 2, 4, not 3.

You have to define a new staff style which applies Slash Notation to the unused layer (3) and shows the other layers.

Define a meta-tool for the new style. It can be useful to have several Slash Notation styles, depending on what's needed (hiding the other layers or not).

Thanks! Yes I finally figured it out. Another important feature that I didn't now about was the "other" choice for staff "appearance" giving the ability to move the slashes up and down by varying the "stem reversal" parameter. I seriously doubt that I ever would have found that without Peter's help in my other post.

I haven't tried Tom's work around yet, but I've tried putting a bottom one-bar repeat in all other layers along with resized notes as cue notes on top with all other layers in a piano part. Still doesn't lower the one-bar repeat. What am I missing?

Top image is what I have in Finale 27, but I want to lower the one-bar repeat like image two. Any ideas?

Perhaps this isn't the right place to voice design ideas but what do you think about: in the Alteration notation box, beside each example or at least slashes, rhythm alt notation and one-bar & two-bar repeats have an up and down arrow to move position and layers instead of moving items from the staff appearance other adjustments?

To get a lower bar repeat symbol, the best way is to define an expression. Type 

Ô and change the font to Maestro 24. Or look for symbol 212.

A Metatool can be assigned to it to speed things up.

P.S. : AFAIK, it seems impossible to define a One Bar Repeat staff style at another height. It would indeed be handy to be able to do it (in a new staff style)