There should be a feature in RCDC whereby you can group selected footing for combine footing design and detailing. Or, after RCDC is finish footing designs and the distance between adjacent footings are below a specified minimum, then RCDC should design those footings as combined footings.
RCDC users who have STAAD.Pro can access the isolated and combined footing modules of SFA 2024. In the opening screen of SFA 2024, select License from the left side of the screen, and choose Basic from the License Selection dialog box. It currently allows the design of isolated footings and combined footings to the ACI and Indian codes.
If you have a license for STAAD Foundation Advanced, you should also be able to design mat foundations.
License selection snaps from SFA 2024 are attached for your reference.