If I understand you correctly, you are trying to get a measure number only at the beginning of each system, not on each and every measure, right?

What I would do:

Measure Tool.

Select All.

Measure menu > Restore Measure Number Defaults

This step will undo “Show Measure Numbers”.

As the next step I would go to

Measure menu (or Document menu) > Edit Measure Number Regions…

and edit the measure number region(s).

You can have different measure number region settings for the score and the linked parts.

The following settings override the measure number settings in the Staff Attributes:

Show On: - Top Staff - Bottom Staff - Exclude Other Staves

Finally, I would examine the Staff Attributes for each staff.

You might prefer to de-select the display of Measure Numbers.

Don’t worry: the measure numbers will still display on the Top Staff (as explained above).

Thank you for your help.

Every measure numbered, Finale  v27.3.0.137, Windows 10, PC - PETER THOMSEN, your trick worked. Every measure was numbered although I had only selected Show Measure Numbers at Start of Staff System in the Edit Measure Number Regions dialogue box, and display Measure Numbers was unchecked in the Staff Attributes dialogue box for each staff.  Your instructions to

(1) Click Measure Tool,

(2) Select all measures,

(3) Click  Measure menu > Restore Measure Number Defaults

did indeed remove the measure numbers.  Then I went back to the Edit Measure Number Regions dialogue box and selected Show Measure Numbers at Start of Staff System again. This time measure numbers only displayed at the beginning of each staff system, as desired.  Thanks!  MakeMusic should include this solution in the User Manual.