Install RGPLua and run this tiny script:
http://carlvine.com/c/time_sig_show.lua

Thanks CARL VINE - this works great!

I've created three additional scripts out of your time_sig_show.lua.  Two for key signatures (show/IfNeeded) and "IfNeeded" for the Time Signature. They all work. I'm just getting into scripting and have a long way to go, but I'm making progress.

I've got two questions:

1. How would the script be modified to toggle between "SHOWSTATE_SHOW" and "SHOWSTATE_IFNEEDED"?

2. Can this type of script work with "SetHideCourtesy()"?  To toggle this item on/off?

When doing student theory worksheets - these are all common items to toggle on/off when creating music examples and/or questions/answer keys, etc.

Check out the script repository at https://www.finalelua.com/scripts. There are lots of handy ideas and you can view the source code immediately and full explanatory guidelines.

You can use one script with lots of different options using "finaleplugin.AdditionalMenuOptions" in a finaleplugin statement. Set a "show_state" variable to be either option and produce separate menus using the one script. With your measure variable "m" set m.HideCautionary to either TRUE or FALSE. Or any of the other variables at https://pdk.finalelua.com/class_f_c_measure.html (RGPLua also offers a "ClassBrowser" to access summaries of this info within Finale).

Thanks - I've been in the weeds on automating measure attributes for a couple of weeks... finally got it. This will make custom theory worksheet creation significantly more efficient.

Combining these scripts together, adding user input, toggling object show/hide, object positioning, creating single measure columns, etc. all possible with one or two clicks.

I'm not a code writer, so it takes me a while - with a lot of trial and error. Thanks again!

Carl thank you so much.  I installed the plugin and the script successfully, and it works.  Thank you!

But, is there a way for me to assign a keyboard shortcut to this, instead of having to search through the Plugins drop-down menu every time I want to use it?  

What I want to be able to do is, select a measure, type Ctrl+T, and then it shows the time signature.

On Mac use Keyboard Maestro - US$36 but worth every cent. On Win try AutoHotKey - free but requires some getting used to. Both are amazing productivity enhancers.

You can also do it very simply with the bult-in Plug-in TG Tools > Menu Shortcuts

Which version of TG Tools is that? (Maybe it's Win-specific)

Just the free, basic version of TG Tools that has been a part of Windows Finale for ages. Don't know about Mac.

That looks excellent. So apparently Win only. (Mac menus are tricky to negotiate).

Michael, thanks.  That TG Tools lets me make a shortcut that opens the Measure Attributes window, but it does not seem to let me make one that shows/hides the key signature in a selected measure.  So it saves me a few clicks but not all the clicks.  Unless I am missing something... ?

Looks like you are not assigning the shortcut to your script. My Lua scripts are in Plug-ins > LuaScript > (here should be your scripts to choose from). If you have installed your script correctly (and apparently you have, since it's working), you need to point to it, as per an example below, wher the schortcut will then execute the script.

YEESSSSSS!!!!!!!!!!!  You guys thank you so much!!!!!!