How to reset Final Cut Pro X viewer window from 41% to Fit?

When you choose "Fit" for the Viewer it will display the scale percentage in order to fit in the Viewer window area. It will also change the percentage dynamically if you resize the Viewer window. If you click the popup, you can see it still has "Fit" checked.

If you "hover" the mouse near the edges of the Viewer, for example, between the storyline and the viewer, or the inspectors on the left or right of the viewer, you should see the cursor change to either:

or

Click the button and drag out the edges of the Viewer. The image will grow or shrink (depending on direction) to fill the new space shape.

Hello!

Have you consulted the user guide?

Thank you very much

@rierikaflower2023 - I did a (very) quick search in the User Guide but didn't see Fit described.

By the way, to universal shortcut to fit anything in a window or timeline is Shift-Z. It’s faster than using menu.

Bonus: Option-Shift-Z fit all clips to vertical zoom in timeline.

Michel