It can be done, but it's a little cumbersome perhaps, depending on how many of these measures you need to convert. The only way I could come up with was this:

select the measure > untilities > change > note durations, from: 16th note to: 1/8th note (un-check rebar music) > OK.
now you have all 1/8th notes (extending into the next bar, but don't worry) > go to Simple Edit > choose 1/8th note + triplet and click on the first 1/8th note and then on the 4th, 7th and 10th note - now you have all 1/8th note triplets.

If you need to do more (with different pitches), you could copy the triplet pattern to wherever you want and then adjust the pitches.

… and then adjust the pitches …

Which can be done easily with the Simple Entry Tool’s Repitch sub-tool.

"I've heard of a JW plugin, ..."

There is, JW Rhythm Copy. I know you said you didn't want to use a plug-in and I commend that but just in case you change your mind. JW Rhythm Copy doesn't mess with the pitches. As Peter Thomsen rightly pointed out ...

"A plug-in only does what you can do yourself, manually”, with Finale.

Only the plug-in does it faster."

Michael, thank you for the detailed instructions. I ALMOST always forget to uncheck the "Rebar Music" box. It would be nice to have the option to turn that off by default.Everything is right with the world, once more.

Peter, I had not seen the "Repitch sub-tool" before. Thank you for opening up yet another door.

Ernest, not that I'm opposed to the plug-in--I have a couple of JW plug-ins and they are great, and I'll get he "Rhythm Copy" for sure. It's just that I want to know how to do it myself.

:-)
Nessa

"It's just that I want to know how to do it myself."

Me too, Kido. Right there with you on that one. MM seems unlikely and unwilling to incorporate any of these concepts natively. Third party plug-in creators are under no obligation to support or create. One reason why some monetary help is a good thing if we are able.

Thanks, Ernest

I've tried to login at JW's site so I can donate, but am unable to so do.
I emailed them and hope to hear.

The JW Plugins have proven invaluable many times.

:-)
Nessa

You don’t need to log on to the site to donate. The login is for developers, as far as I know. You can just send the donation via PayPal. That’s how I’ve always done it, anyway.

Nessa, our lose if Mr. Williamsson doesn't want to create or update but at least he has kept the web site open for d/l. I do hope he is doing well. He has contributed so much to the Finale community.

If MM doesn't want to or see the need to, perhaps somebody like Jan Angermüller could take over the plug-ins. He is a genius plug-in developer.

"I've tried to login at JW's site so I can donate,  ..."

I don't think you need to log-in to donate there used to be a "Donate" button that took you to Paypal or your CC.

Thank you, Mike and Ernest,

Good to know I can still donate.

Hope someone will continue their great legacy.
:-)
Nessa