How can I modify navigation bar in subform spreadsheet so that I can see the navigation arrows?
It depends of the theme of your desktop. Have a look here:
Seems you are using dark mode as theme of your desktop.
You could show the table control without navigation bar and switch to a separate navigation bar:
Table control doesn’t work well with dark mode. There is no possibility to set the colors right way for background of navigation buttons and text content like “Records”. Nothing could be changed for Form controls and Base through the custom colors.
You system runs with dark mode.
Set Scheme: ‘LibreOffice’ and Automatic: ‘Light’
or add a separate navigation bar (could be found under form controls) at the bottom of the table-control.
Don’t know if it will work in a better way. Have never tried dark mode on any system here.