Currently each expansion card has only one port.
But in some cases there seems to be more than enoguh space to add more ports.
Like the Audio Expansion Card. Or a double USB-C ports expansion cards.
Or a multi card reader expansion card.
Etc.
Welcome to the forum.
There are a few threads with discussions on multi-port cards. Some like a thread on a double USB-C card has details on efforts to make cards.
The TL;DR is, there is not at all as much room as it seems from the outside. Just the ports themselves can take up more room than one thinks, on the inside. Then shell eats some space, more by necessity of the guide rails.
Full-featured dual usb-C is unfortunately rather complicated and the components would either take up too much room, or require a lot of time & effort or skill to even try to fit. So for that card, I wouldn’t suggest anyone holds their breath waiting. A limited feature and no PD, dual usb-C, that we might see.
The problem is the room left for the electronics after you assign space for the connectors. The connectors take up a significant amount of room, and then there is at least one IC required, often two, plus some passive components.
If you work your way back through the postings somebody did do a dual USB-C, but you could not charge the laptop through it as that was just too much circuitry required to deal with the USB-PD requirements.
That, at least, has been done!
I made an sd/micro sd combo card at usb 2.0 speeds a while ago: SD + MicroSD Expansion Card