You don’t need “conditional print expression”.
The page number usually goes inside the header or footer of the page. Footer/header are attributes of the page style in use.
Open the styles side pane with F11
and select the page styles (fourth icon from left in the toolbar). The style in use is highlighted (likely to be /Default Style in your case). Right-click on it and Modify
.
Got to the Header
or Footer
tab. Enable it. Uncheck Same content on first page.
Now you have an independent header or footer for the first page. Put the page number field in the header/footer of the first page and nothing in the header/footer of page 2. Your page number appears only on the first page.
You can also proceed vice versa, i.e. no page number on first page and page number on pp. 2+.
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