What the title says. Two whole notes to a measure, but I want the time signature displayed as C with a bar through it.
See this, a similar approach should work in your case: https://www.steinberg.net/forums/viewtopic.php?t=154465
It’s easier than that for your case, as setting it for cut-common (rather than common, as that thread refers to) is straightforward and does not require a workaround. Use a 4/2 time signature, rather than 2/1, and then use the ‘Common/Cut common’ property when the time signature is selected.
Any size bar with 2 as the denominator can be set as Cut C from the properties panel.