To create it : it looks like you are almost there. It can be done in the Score Manager or in a new Staff Style :  -> Staff -> Other. In the Staff Setup window, select Custom. Then click on the boxes left of the staff to add or to delete staff lines.

To save it : you can make a template including this staff, or if it is a staff style, save a Library (of staff styles) via the File menu to reload it into other documents. To avoid duplicates, make a library which only has that staff style, because when you load it into another file, it will be added to the existing ones.

Michel,

Thank you for helping me.

Any staff style I create in the Custom Stuff will be rejected by the Reset Staff To at the bottom. I could not Save it neither to put in a library.

I will go the Score Manager to see if it works.

Barat

I tried to create a staff style, in Finale 2012 and v.25, and it works without a problem. "Reset Staff To" doesn't seem to have an effect as long as Custom is selected. Here is what I see : 

I checked the Custom Staff as you did, see no result by clicking OK

Somehow it did work through ScoreManager. Now I have my own custom staff. Thank you Michel.

I was able to do it in the Score Manager as you did (this applies to the whole staff) and as a staff style, locally, too (Staff Menu, Define Staff Style etc...). I was going to attach a couple of files here, but at first sight, I can't attach .mus files !

Here is a screenshot, at least...(staff style)

Michel,

After I created a desired custom staff, I found the notes are not the same anymore. Can we change the pitch/sound of original C to D?

Please explain more precisely what you want to achieve. Is this a playback issue ? I have no idea what notes such a staff will produce, with the double spaces etc... Is this for a single or for multiple instruments ? Please draw a sketch with where the notes actually are and how you want things...

Michel,

I found this is a separate issue. Let me do more study to come up with clearer idea.